What’s Vulnerable › Vulnerabilities

CVE-2026-104086: 7-Zip < 26.03 SquashFS Uninitialized Memory Disclosure via UID/GID Table

• Severity: medium (CVSS 5.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-14 · updated 2026-10-19
• Weakness: CWE-908

Description

7-Zip before 26.03 contains an uninitialized memory disclosure vulnerability in the SquashFS v4 archive handler (SquashfsHandler.cpp) that allows attackers to leak heap memory by crafting a malicious archive where the superblock’s no_ids field is set so that the final metadata block’s expected size is miscomputed and bypasses the size validation check. By listing or extracting the crafted archive, attackers can cause the application to return uninitialized heap memory as the kpidUserId and kpidGroupId properties, exposing potentially sensitive process memory contents to the user.

Affected products

• 7-Zip: before 26.03 — fixed in 26.03

How to fix

Upgrade to a fixed version: 7-Zip 26.03. Check the vendor advisory for mitigations.

References

• https://7-zip.org/
• https://sourceforge.net/p/sevenzip/discussion/45797/thread/db6922e1d0/
• https://www.vulncheck.com/advisories/7-zip-squashfs-uninitialized-memory-disclosure-via-uid-gid-table

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