CVE-2026-57204: pypdf: Missing stream length values ignore defined limits

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-06-30 · updated 2026-10-25
Weakness: CWE-400

Description

pypdf is a free and open-source pure-python PDF library. Prior to 6.13.3, a maliciously crafted PDF can cause DoS. An attacker who uses this vulnerability can craft a PDF which leads to large memory usage, as MAX_DECLARED_STREAM_LENGTH is sometimes ignored. This requires parsing a content stream without a /Length value. This issue has been fixed in version 6.13.3.

Affected products

py-pdf pypdf: before 6.13.3 — fixed in 6.13.3

How to fix

Upgrade to a fixed version: py-pdf pypdf 6.13.3. Check the vendor advisory for mitigations.

References

https://github.com/py-pdf/pypdf/releases/tag/6.13.3
https://github.com/py-pdf/pypdf/security/advisories/GHSA-jm82-fx9c-mx94

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