CVE-2026-29509
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedPatool 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidencePatool before 4.0.5 has a path traversal vulnerability in safe_extract() where is_within_directory() uses os.path.commonprefix() for character-level string comparison instead of proper path-level comparison. This allows malicious archive entries with crafted paths like 'evil/../file.txt' to bypass containment checks and write files outside the intended extraction directory.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Verify patool is installedRun 'pip show patool' or 'python -c "import patool"' to confirm patool is present in your Python environmentAffected if patool is not installed or cannot be imported - not affected
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Determine installed patool versionRun 'pip show patool' and note the Version field, or 'python -c "import patool; print(patool.__version__)"'Affected if version is below 4.0.5 - vulnerable to path traversal
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Identify use of safe_extract()Search your codebase for calls to patool.extract_archive() with archive passwords, or grep for 'safe_extract' and 'is_within_directory' in patool sourceAffected if code uses patool to extract archives, particularly password-protected ones via extract_archive() - the vulnerable code path may be reached
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Confirm extraction of untrusted archivesReview whether patool is used to extract archives from untrusted sources (downloads, user uploads, email attachments)Affected if extracting untrusted archives with patool versions below 4.0.5 - vulnerable to CVE-2026-29509
You are affected if patool version is below 4.0.5 AND you use it to extract archives from untrusted sources, as the flawed os.path.commonprefix() check in is_within_directory() can be bypassed with paths like 'evil/../file.txt'.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scopedUpgrade patool to version 4.0.5 or later, which implements proper path-level comparison in the containment check. If upgrading is not immediately possible, validate and sanitize all archive member paths before extraction.
patool >= 4.0.5
- Upgrade patool to version 4.0.5 or later using pip: pip install --upgrade patool
- Verify the installed version: pip show patool
- Ensure you are running Python 3.12 or later for additional protection (if possible), as the vulnerability only affects Python versions before 3.12
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation1.0 h
- Implementation1.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,376.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-29509 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-29509 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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