Vulnerability in 7-Zip
CVE-2026-104086
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.
Published .
CVSS v3 metric
CVSS v3 base score 5.5 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- 7-zip.org/ (product)
- sourceforge.net/p/sevenzip/discussion/45797/thread/db6922e1d0/ (release-notes, patch)
- www.vulncheck.com/advisories/7-zip-squashfs-uninitialized-memory-disclosure-via… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-104086?
- CVE-2026-104086 is a medium-severity vulnerability in 7-Zip, classified under Use of Uninitialized Resource. CVSS score: 5.5/10. Published 2026-10-14.
- How severe is CVE-2026-104086?
- Medium severity. CVSS v3 base score is 5.5 out of 10.