# CVE-2026-29509: Patool < 4.0.5 Path Traversal via safe_extract() Function

> Attackers can write arbitrary files via malicious archives due to flawed path validation in Patool's extraction function.

- **Severity:** Medium 5.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 26 Jun 2026
- **Updated:** 14 Jul 2026
- **Also known as:** DEBIAN-CVE-2026-29509, GHSA-p95f-9f9h-wwvh, MGASA-2026-0504, UBUNTU-CVE-2026-29509

## What is CVE-2026-29509?

CVE-2026-29509 is a medium-severity path traversal vulnerability in wummel patool, published on 26 Jun 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

Patool before 4.0.5 contains a path traversal vulnerability in the safe_extract() function in patoolib/programs/py_tarfile.py when running on Python before 3.12, where the is_within_directory() helper uses os.path.commonprefix() for character-level string comparison instead of path-level comparison, allowing a crafted archive member path to bypass the containment check. Attackers can supply a malicious archive with specially crafted member paths to write arbitrary files.

Weakness: CWE-22 (Improper Limitation of a Pathname to a Restricted Directory)

## Which versions are affected by CVE-2026-29509?


## How do I fix CVE-2026-29509?

Upgrade to a fixed version.

## Is CVE-2026-29509 being exploited?

There is no known exploitation of CVE-2026-29509 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-29509 and fix it if it is affected.

What it is: CVE-2026-29509 is a medium-severity path traversal vulnerability in wummel patool, published on 26 Jun 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-29509 in the wild and no public exploit code.

Affected product: wummel patool. 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-2026-29509/ (Markdown: https://insights.sbomify.com/CVE-2026-29509/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-29509
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-29509
- OSV: https://osv.dev/vulnerability/CVE-2026-29509

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-29509/
Summaries are generated and may contain mistakes; the official description above is the record.