PyPDF2 vulnerable to possible Infinite Loop when reading malformed objects

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

6.2 · CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2023-36807: 0.57% estimated exploitation activity in the next 30 days; percentile 47.40 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact An attacker who uses this vulnerability can craft a PDF which leads to an infinite loop. This infinite loop blocks the current process and can utilize a single core of the CPU by 100%. It does not affect memory usage. That is, for example, the case if the user extracted metadata from such a malformed PDF. Patches The issue was fixed with https://github.com/py-pdf/pypdf/pull/1331 Workarounds If you cannot update your version of PyPDF2 (preferably to pypdf3.1.0 as PyPDF2 is deprecated), you should modify PyPDF2/generic/datastructures.py::readobject. Replace: by References pypdf issue #1329 pypdf PR #1331

Published by the source

30 Jun 2023, 22:19 UTC

Last modified by the source

7 Jul 2026, 17:56 UTC

Source last checked

26 Oct 2026, 13:12 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-hm9v-vj3r-r55m

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-hm9v-vj3r-r55m

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# Patch Next advisory brief: CVE-2023-36807

Advisory: PyPDF2 vulnerable to possible Infinite Loop when reading malformed objects
IDs: CVE-2023-36807, GHSA-hm9v-vj3r-r55m
Record: https://patchnext.com/advisories/cve-2023-36807 (revision 2, source checked 26 Oct 2026, 13:12 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: pypdf2 2.10.6. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI pypdf2: affected >= 2.10.5, <= 2.10.5; fixed in 2.10.6

## Suggested inspection (read-only)
- `python -m pip show pypdf2`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on pypdf2.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-hm9v-vj3r-r55m (OSV record GHSA-hm9v-vj3r-r55m lists affected ranges: PyPI pypdf2 >=2.10.5 <2.10.6 (fixed))
- Verified: https://github.com/advisories/GHSA-hm9v-vj3r-r55m (GitHub-reviewed advisory GHSA-hm9v-vj3r-r55m lists affected ranges: PyPI pypdf2 >=2.10.5 <=2.10.5)

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