CVE-2026-104086 7-Zip < 26.03 SquashFS Uninitialized Memory Disclosure via UID/GID Table
Attackers can leak sensitive heap memory by crafting malicious SquashFS archives, exposing process memory contents to users of 7-Zip.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-104086?
CVE-2026-104086 is a medium-severity vulnerability in 7-Zip, published on 14 Oct 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Official 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.
Weakness: CWE-908
Which versions are affected by CVE-2026-104086?
How do I fix CVE-2026-104086?
Upgrade to a fixed version.
Is CVE-2026-104086 being exploited?
There is no known exploitation of CVE-2026-104086 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-104086, ECHO-1f60-4fc3-315e, GHSA-xhq8-p89q-r47c, UBUNTU-CVE-2026-104086.