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pypdf: Possible long runtimes for large xref table header limitsGHSA-gmh7-3g9r-mjh5

Fix: py-pdf/pypdf#4239

GHSA-gmh7-3g9r-mjh5 is a CWE-834 vulnerability in pypdf. A fix is available for pypdf — see the affected versions and patch details below.

Also known asCVE-2026-115580
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 24, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
0.5%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs44th percentile — riskier than 44% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected
🐍pypdf

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

Impact

An attacker who uses this vulnerability can craft a PDF which leads to long runtimes. This requires opening a file with large/wrong upper limits in the xref table.

Patches

This has been fixed in pypdf==6.21.2.

Workarounds

If you cannot upgrade yet, consider applying the changes from PR #4239.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐍PyPIpypdfall versions6.21.2pip install --upgrade 'pypdf==6.21.2'

Detection & mitigation playbook

Open-source dependency
  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pypdf, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update pypdf to 6.21.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-gmh7-3g9r-mjh5 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

### Impact An attacker who uses this vulnerability can craft a PDF which leads to long runtimes. This requires opening a file with large/wrong upper limits in the xref table. ### Patches This has been fixed in [pypdf==6.21.2](https://github.com/py-pdf/pypdf/releases/tag/6.21.2). ### Workarounds If you cannot upgrade yet, consider applying the changes from PR [#4239](https://github.com/py-pdf/pypdf/pull/4239).
O3 Security · Impact-Aware SCA

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