# 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.

- **Severity:** Medium 6.8 (`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`)
- **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:** Yes
- **Published:** 14 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-104086, ECHO-1f60-4fc3-315e, GHSA-xhq8-p89q-r47c, UBUNTU-CVE-2026-104086

## 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 (Use of Uninitialized Resource)

## 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.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-104086 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-104086 in the wild and no public exploit code.

Affected product: 7-Zip. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-104086/ (Markdown: https://insights.sbomify.com/CVE-2026-104086/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-104086
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-104086
- OSV: https://osv.dev/vulnerability/CVE-2026-104086

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-104086/
Summaries are generated and may contain mistakes; the official description above is the record.