CVE-2026-31826: pypdf: manipulated stream length values can exhaust RAM

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-03-10 · updated 2026-06-17
Weakness: CWE-770

Description

pypdf is a free and open-source pure-python PDF library. Prior to 6.8.0, an attacker who uses this vulnerability can craft a PDF which leads to large memory usage. This requires parsing a content stream with a rather large /Length value, regardless of the actual data length inside the stream. This vulnerability is fixed in 6.8.0.

Affected products

py-pdf pypdf: before 6.8.0 — fixed in 6.8.0

How to fix

Upgrade to a fixed version: py-pdf pypdf 6.8.0. Check the vendor advisory for mitigations.

References

https://github.com/py-pdf/pypdf/pull/3675
https://github.com/py-pdf/pypdf/releases/tag/6.8.0
https://github.com/py-pdf/pypdf/security/advisories/GHSA-hqmh-ppp3-xvm7

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