Researchers have identified a significant zero-day vulnerability in the 7-Zip archiving utility that was actively exploited as part of Russia’s ongoing invasion of Ukraine. The flaw enabled a Russian cybercrime operation to bypass Windows protections designed to limit the execution of files downloaded from the Internet. Specifically, the attack leveraged the Mark of the Web (MoTW) mechanism, a protective feature that adds a Zone.Identifier data stream to Internet-downloaded files, triggering additional scrutiny by Windows Defender SmartScreen and imposing execution restrictions. The vulnerability, tracked as CVE-2025-0411, was addressed with the release of 7-Zip version 24.09 in late November, but the period before the patch saw active exploitation that underscored the risk of double-encapsulated archives and deception through file masquerading. This article provides a comprehensive, field-tested look at how the exploit worked, who was targeted, what security defenses were circumvented, and what steps organizations and individual users should take to mitigate similar threats in the future.
Technical overview: how CVE-2025-0411 operated within 7-Zip and Windows defenses
At the core of the vulnerability was a breakdown in how 7-Zip propagated Mark of the Web protections when archives were nested and then chained to host executable content. The MoTW mechanism relies on a Zone.Identifier alternate data stream attached to files downloaded from the Internet or retrieved from network shares. When present, Windows applies additional scrutiny to the file, and execution is subject to restrictions designed to curb auto-execution of potentially dangerous content. Under normal circumstances, Windows analyzes the Zone.Identifier tag and determines whether to prompt the user, block execution, or allow it with warnings. The MoTW tag is a powerful, user-facing security signal that helps prevent users from inadvertently running malware downloaded from untrusted sources.
The zero-day exploited a chain where an executable was embedded within an inner archive, which itself was embedded in an outer archive carrying the MotW tag. In this arrangement, the outer archive inherited the MoTW tagging, but the inner archive did not receive the same tag propagation. Consequently, when Windows evaluated the payload, the inner archive and its contained executable were not properly covered by the MoTW protections. This discrepancy created a vulnerability window in which malicious payloads could bypass the intended safeguards and run with reduced or no MoTW scrutiny. The exploitation was not a single-file trick; it relied on a multi-layer encoding that caused the protection to be unevenly applied across nested containers. The vulnerability was formally tracked as CVE-2025-0411 and was specifically mitigated by the release of 7-Zip version 24.09.
Security researchers described the root cause as the prior failure of 7-Zip to consistently propagate MoTW protections to the content of double-encapsulated archives. In practice, this meant threat actors could create archives containing malicious scripts or executables that would not receive MoTW protections, rendering Windows users more vulnerable than expected. This oversight allowed attackers to deliver payloads that appeared under MoTW’s protective umbrella because the outer archive carried the tag, while the critical inner content did not. The patch implemented in version 24.09 corrected the propagation of MoTW protections so that nested archives would maintain consistent removal or enforcement of restrictions on execution. The fix thus restored the integrity of MoTW’s protective behavior when dealing with multi-layer archives.
The attackers also adopted a tactic designed to increase the likelihood of user interaction and successful delivery: the use of homoglyphs. Homoglyphs are characters that visually resemble standard ASCII characters but belong to different character sets or encodings. A familiar example is the Cyrillic Cyrillic С, which looks nearly indistinguishable from the Latin letter C but is encoded differently. By rendering executable file extensions with homoglyphs, threat actors could disguise executables as document files or other benign formats, thereby increasing the chances that recipients would open attachments and trigger execution. This technique was employed to make double-archived payloads appear less suspicious and more credible to recipients navigating through a busy inbox or a compromised account.
In the broader attack chain, the attackers used legitimate-looking email workflows and compromised accounts to attach the double-archived payloads to messages. The emails purportedly came from genuine accounts associated with Ukrainian government agencies, lending a veneer of legitimacy to the communications and increasing the probability that targets would download and unzip the archives. This social engineering dimension strengthened the overall attack, marrying technical vulnerability with human factors to maximize impact. While the exact nature of the embedded scripts or executables varied, the operational pattern consistently leveraged the absence of MoTW coverage in the inner archive to bypass Windows protections and execute payloads on victims’ machines.
MoTW, Windows SmartScreen, and the defense landscape during the incident
A central aspect of the incident was the interplay between MoTW and Windows Defender SmartScreen. MoTW is designed to prevent users from accidentally executing files downloaded from the Internet by flagging them and prompting the user before execution. SmartScreen adds an additional gate to intercept potentially unsafe downloads and running content. When MoTW is properly applied to all content within an archive, even embedded or nested payloads should be subject to scrutiny, reducing the risk that a user inadvertently runs a dangerous executable. The exploitation of double-encapsulated archives revealed a gap in the propagation of MoTW protections when archives are nested multiple times. The vulnerability exploited precisely this gap, letting malicious content escape MoTW checks depending on how the inner payload’s tags were inherited during extraction.
The patch to 7-Zip version 24.09 addressed this subspecies of MoTW propagation failures. By ensuring consistent MoTW propagation across nested archives, the software prevents malicious payloads from piggybacking on the outer archive’s MoTW status while quietly evading protection on inner contents. In practical terms, this means that, after the patch, Windows users and systems that properly scan nested archives will have an increased probability of MoTW coverage applying to every layer of a double- or triple-archived payload. The patch, combined with standard Windows Defender SmartScreen behavior, strengthens the multi-layer defense against these complex packaging attacks.
From an organizational security perspective, the incident highlighted the importance of ensuring that security controls extend to all file formats and packaging structures used within an organization. Archive managers and security teams must account for nested archives, alternate data streams, and any method attackers might use to conceal the true nature of a payload. The patch serves as a reminder that protections such as MoTW are only as effective as their implementation across all possible data structures. It also underscores the need for defense-in-depth measures that do not rely solely on file-level protections but also include network monitoring, endpoint detection, and user education to identify suspicious attachments and unconventional delivery chains.
The double-encapsulation tactic: how nested archives bypassed protections
Double-encapsulation refers to archiving content inside one archive, which is then archived again inside a second archive. In the context of this vulnerability, attackers exploited a mismatch in how MoTW protections were applied when a file inside an inner archive did not receive the MoTW tag, even though the outer archive did. This discrepancy allowed a malicious payload to slip past MoTW and Windows SmartScreen defenses as long as the user opened and extracted the outer archive, thereby exposing the inner payload to execution.
The practical effect of this tactic was that a user could receive a seemingly safe or legitimate outer archive that had MoTW applied to its outermost contents, while the inner content—where the actual malicious executable resided—remained free of MoTW restrictions. Once the user extracted the inner archive, the payload could execute without triggering MoTW-based defense signals, provided the user executed or opened the inner file. The vulnerability’s design leveraged a combination of nested packaging and the specific behavior of 7-Zip’s archive handling prior to the patch to ensure the inner payload did not inherit the protective tagging.
Trend Micro researchers identified this root cause in their analysis, explaining that the double-encapsulation approach exploited the way 7-Zip propagated MoTW protections before the 24.09 update. The researchers stressed that threat actors could craft archives that render malicious scripts or executables invisible to MoTW protections, thus enabling Windows users to become targets of drive-by downloads or carefully staged phishing campaigns. The fix implemented in 24.09 closes this loophole by ensuring that MoTW protections propagate consistently to content inside double-encapsulated archives, reinforcing a more reliable defense when dealing with nested archives and reducing the likelihood that inner content escapes scrutiny.
The timeline around the vulnerability’s disclosure and patch release underscores the importance of timely software updates. The vulnerability was fixed with the release of 7-Zip version 24.09 in late November, covering the critical propagation gap identified by researchers. Users who applied the patch closed the primary avenue used by the attackers to bypass MoTW protections and significantly reduced the risk to Windows systems that regularly process archives. The incident illustrates how a relatively small technical oversight—PoTW propagation in nested archives—can be exploited at scale when coupled with refined social engineering, targeted distribution, and the exploitation of real-world geopolitical tensions.
Targeted campaigns: a look at the Ukrainian agencies and related entities
The attackers’ campaign involved a range of Ukrainian government and public-sector entities, with a focus on entities that could be considered sensitive from a security and operations standpoint. The scope of targets included the following organizations and institutions, which were cited in security analyses as having been compromised or targeted in the attack sequence:
- State Executive Service of Ukraine (SES) – Ministry of Justice
- Zaporizhzhia Automobile Building Plant (PrJSC ZAZ) – Automobile, bus, and truck manufacturer
- Kyivpasstrans – Kyiv Public Transportation Service
- SEA Company – Appliances, electrical equipment, and electronics manufacturer
- Verkhovyna District State Administration – Ivano-Frankivsk oblast administration
- VUSA – Insurance company
- Dnipro City Regional Pharmacy – Regional pharmacy
- Kyivvodokanal – Kyiv Water Supply Company
- Zalishchyky City Council – City council
The use of compromised government accounts to attach double-archived payloads suggests a high degree of operational discipline and a focus on obtaining credible-looking attachments to lower the suspicion threshold for recipients. The targeting of state services such as SES and ministries, as well as critical infrastructure entities like Kyivvodokanal and Kyivtrans, underscores an intent to disrupt essential services or to harvest credentials and access that could support broader espionage or financially motivated activities. In addition to government bodies, the inclusion of manufacturing and utility entities reveals a strategic emphasis on industries that underpin daily life and regional stability. The attackers’ approach also demonstrates that threat actors understood the value of presenting attachments as legitimate, leveraging both the MoTW tag on outer archives and the absence of MoTW on inner content to create a sense of normalcy around the file, thereby increasing the chance that recipients would engage and execute the payload.
For defenders, this targeted pattern signals a need to heighten scrutiny of emails that appear to come from compromised accounts or legitimate-looking organizations, particularly when they involve attachments that purport to be archives with nested content. It also points to the importance of verifying the provenance of attachments, employing robust email security gateways, and ensuring that users practice cautious handling of unsolicited messages—even those that appear to originate from trusted domains or familiar institutions. The lesson is clear: attackers are layering social engineering with sophisticated exploitation techniques, and organizations must implement comprehensive countermeasures that address both human behavior and technical vulnerabilities.
Security community analysis: attribution, findings, and implications
Security researchers from Trend Micro provided a detailed analysis of the vulnerability’s root cause and its exploitation method. They explained that the core issue lay in the failure to propagate MoTW protections to the content of double-encapsulated archives prior to the release of version 24.09. This oversight allowed threat actors to craft archives in which the outer container appeared to be safeguarded by MoTW, while the inner content escaped those protections. The resulting discrepancy created an exploitable gap in the MoTW enforcement mechanism that attackers could exploit to deliver malicious payloads with a reduced risk profile on execution. The researchers emphasized that the vulnerability’s exploitability depended on the particular packaging structure and the presence of a double-archival chain, which is not uncommon in large-scale phishing campaigns where attackers attempt to maximize the odds of payload delivery.
Trend Micro’s assessment, conveyed through the research team’s findings, highlighted the significance of robust archive handling across tools used by end users. The findings also underscored the importance of ensuring that security controls extend to nested and multi-layer file packaging scenarios. The release of 7-Zip 24.09 represented a critical improvement, closing a substantial gap that could be exploited by attackers to bypass MoTW protections and Windows defenses. The broader implication for the security community is a reminder that defense must anticipate increasingly complex delivery chains, including layered archives and obfuscated or masqueraded content. Analysts also highlighted that the use of homoglyphs as a disguise for executable files remains a persistent tactic in phishing and malware distribution, warranting continued attention to character-by-character analysis as part of anti-malware monitoring and email filtering.
From an organizational viewpoint, the analysis reinforces the importance of diligent software maintenance, timely upgrades, and the adoption of defense-in-depth strategies. While the 24.09 patch closes the direct MoTW propagation gap for double-encapsulated archives, it does not eliminate all vectors through which attackers may attempt to deliver payloads. Enterprises should combine software updates with user education, strict email hygiene, secure configuration baselines, and endpoint protection that can detect suspicious archive contents or anomalous extraction behavior. The case also demonstrates the value of threat intelligence sharing and cross-vendor collaboration in rapidly identifying, understanding, and mitigating innovative exploitation techniques that blend technical vulnerability with real-world social engineering.
Patch details, timelines, and practical guidance for users and organizations
The fix for CVE-2025-0411 was embedded in 7-Zip version 24.09, released in late November. This update addressed the propagation gap by ensuring MoTW protections are consistently enforced across all levels of nested archives, thereby preventing the inner content from escaping MoTW scrutiny. For users and organizations, several practical steps emerge from this timeline:
- Update to 7-Zip version 24.09 or later as soon as possible to ensure double-encapsulation is fully covered by MoTW protections.
- Exercise caution with archives that arrive via email, especially when attached to messages that appear to come from compromised or legitimate-looking organizational accounts.
- Maintain a layered security approach: rely not solely on MoTW but also on Windows Defender SmartScreen, trusted path monitoring, and robust email filtering to identify suspicious attachments or unusual packaging structures.
- Implement user education programs that emphasize the risks of opening archive attachments, particularly when presented in contexts that lend credibility to the sender or organization.
- Deploy network and endpoint defenses capable of detecting and blocking patterns associated with double-archived payloads, including unusual archiving practices and anomalous extraction behavior.
- Regularly review and update security baselines for file handling, including policies around downloaded content, archive extraction, and execution controls for nested payloads.
The November patch date also provides organizations with a practical deadline to re-audit past communications and attachments that could have exploited this vulnerability. Security teams should verify that their back-end processes and endpoint protection configurations are aligned with the new MoTW propagation behavior and that any automated workflows that rely on archive unpacking are updated to conform with the corrected policy. The patch reinforces the idea that keeping software in current, supported versions is central to maintaining an effective security posture against evolving exploitation techniques that combine packaging tricks with geopolitical-tinged social engineering.
Operational takeaways: defending against similar threats in the future
Beyond applying the patch, organizations should implement a robust, multi-layered defense approach to mitigate the risk of similar threats. First, ensure comprehensive defense-in-depth coverage that includes advanced threat protection for archiving tools, robust endpoint detection, and continuous monitoring for suspicious file packaging patterns. Second, strengthen email security with filtering that flags nested or seemingly innocuous archives, especially those with letters or characters that resemble legitimate domains or organizations. Third, provide ongoing security awareness training for staff to recognize signs of social engineering and the potential for compromised accounts to be used in attachment-based campaigns. Fourth, enforce strict application control or whitelisting for archiving tools and their associated executables, thereby reducing the risk of unapproved payloads executing on endpoints. Fifth, adopt a policy of prompt patch management, monitoring vendor advisories, and implementing security updates in a timely manner to close known vulnerabilities before they can be weaponized.
In addition, organizations should consider implementing integrity checks for downloaded content, such as checksums or digital signatures, to verify the authenticity and integrity of archives before they are opened. This approach helps guard against tampered archives that might be delivered with similarly masquerading characteristics, including homoglyph-based disguises. A proactive security posture also benefits from ongoing threat intelligence sharing and collaboration among security teams, vendors, and researchers, allowing for rapid dissemination of indicators of compromise and best practices in response to emerging attack patterns that leverage nested packaging and MoTW-related gaps.
Conclusion
The 7-Zip CVE-2025-0411 vulnerability represented a sophisticated intersection of packaging technique, Windows protection mechanisms, and attacker ingenuity. By exploiting a propagation gap in MoTW protections for double-encapsulated archives, a Russian cybercrime group could bypass safeguards and deliver malicious payloads to Windows users. The attackers augmented their technical approach with homoglyph-based disguises and social engineering that leveraged compromised accounts associated with Ukrainian government and related organizations, underscoring the importance of a multi-faceted defense strategy in both the technical and human dimensions of security. The late November patch, 7-Zip version 24.09, closed the core vulnerability by ensuring consistent MoTW propagation across nested archives, reinforcing the broader security posture against similar packaging-based threats.
Organizations and individuals should remain vigilant and proactive about updates, archive handling practices, and comprehensive security controls to reduce the risk of recurrence. The incident serves as a reminder that even well-established protections can be undermined by edge-case behaviors in data handling, and it highlights the enduring need for ongoing research, timely patching, and layered defenses to protect against increasingly sophisticated threat landscapes. By applying the lessons learned from this vulnerability and maintaining a robust security program, users can better defend themselves against evolving attack techniques that blend technical exploits with targeted social engineering.
