CVE-2026-104086 7-Zip CVE debrief

Who should care

Defenders responsible for systems that process archives from untrusted sources should be aware of this vulnerability. This includes administrators of servers, workstations, and any system that uses 7-Zip for archive processing. Updating to version 26.03 or later is crucial to mitigate this vulnerability.

Why it matters

CVE-2026-104086 is a medium-severity vulnerability in 7-Zip that allows attackers to leak heap memory by crafting malicious SquashFS v4 archives. Defenders should prioritize updating 7-Zip to version 26.03 or later, especially for systems processing archives from untrusted sources. The vulnerability's impact is limited to potential memory disclosure and does not support claims of arbitrary code execution or data theft.

• Potential exposure of sensitive process memory contents
• Possible data leakage through uninitialized heap memory disclosure
• Need for verification of 7-Zip version and exposure to untrusted archives
• Priority on updating 7-Zip to version 26.03 or later

Technical summary

The SquashFS v4 archive handler in 7-Zip before 26.03 is vulnerable to an uninitialized memory disclosure. By crafting a malicious archive with a manipulated superblock's no_ids field, attackers can bypass size validation checks and cause the application to leak heap memory when listing or extracting the archive. This vulnerability affects systems that process archives from untrusted sources, and defenders should prioritize updating 7-Zip to version 26.03 or later to mitigate this vulnerability. The vulnerability's impact is limited to potential memory disclosure and does not support claims of arbitrary code execution or data theft. Affected product deployments should be reviewed, and compensating controls for

Defensive priority

Defenders should prioritize updating 7-Zip to version 26.03 or later to mitigate this vulnerability. Systems that process archives from untrusted sources are at higher risk and should be updated immediately.

Recommended defensive actions

• Update 7-Zip to version 26.03 or later
• Restrict processing of archives from untrusted sources
• Monitor systems for unusual memory access patterns
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The vulnerability is confirmed in 7-Zip versions before 26.03. The CVE Program and NVD provide official records of this vulnerability. However, details about potential exploitation or specific impacts are limited in the provided source corpus.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.