MEDIUM6.2

PYSEC-2026-1837

PyPDF2 quadratic runtime with malformed PDF missing xref marker

Quick fix

PYSEC-2026-1837 — pypdf2: upgrade to the fixed version with the command below.

pip install --upgrade 'pypdf2>=1.27.9'

Details

### Impact An attacker who uses this vulnerability can craft a PDF which leads to unexpected long runtime. This quadratic runtime blocks the current process and can utilize a single core of the CPU by 100%. It does not affect memory usage.

### Patches https://github.com/py-pdf/pypdf/pull/808

### Workarounds _Is there a way for users to fix or remediate the vulnerability without upgrading?_

### References * [PyPDF2 PR #808](https://github.com/py-pdf/pypdf/pull/808) * [PyPDF2 Issue #582](https://github.com/py-pdf/pypdf/issues/582)

Are you affected?

Enter the version of the package you're using.

Affected packages

PyPI/pypdf2

Introduced in: 0Fixed in: 1.27.9

Fixpip install --upgrade 'pypdf2>=1.27.9'

References

https://github.com/py-pdf/pypdf/security/advisories/GHSA-jrm6-h9cq-8gqw[WEB]
https://nvd.nist.gov/vuln/detail/CVE-2023-36810[ADVISORY]
https://github.com/py-pdf/pypdf/issues/582[WEB]
https://github.com/py-pdf/pypdf/pull/808[WEB]
https://github.com/py-pdf/pypdf/commit/c6c56f550bb384e05f0139c796ba1308837d6373[FIX]
https://github.com/py-pdf/pypdf[PACKAGE]
https://lists.debian.org/debian-lts-announce/2023/07/msg00019.html[WEB]
https://pypi.org/project/pypdf2[PACKAGE]
https://github.com/advisories/GHSA-jrm6-h9cq-8gqw[ADVISORY]