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Advisory record · GHSA-m449-cwjh-6pw7

pypdf's LZWDecode streams be manipulated to exhaust RAM

CVSS 6.6 MediumEPSS 0.0039 · 33rd percentile

Published by the GitHub Advisory Database at 24 Nov 2025, 22:42 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
pypdfPyPI<6.4.06.4.0
Identifiers
GHSA-m449-cwjh-6pw7 · CVE-2025-66019 · PYSEC-2026-1832
Weakness (CWE)
CWE-400 · CWE-409
Tags
Published
24 Nov 2025
Updated
10 Sept 2026

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

The pypdf package before 6.4.0 can be made to use up to 1 GB of memory per stream when parsing a page's content stream that uses the LZWDecode filter. An attacker can do this by supplying a crafted PDF, which can exhaust RAM. Upgrade pypdf to 6.4.0 or later. The source gives a workaround that involves changing a default limit in code, but it is not described in detail here.

Written 5 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

ScoreRatingCVSSVectorSource
6.6 Medium 4.0 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U CNA (GitHub_M)
  • CISA KEV Not listed.
  • EPSS 0.0039, the 33rd percentile, on 6 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 31 Oct 2026, 14:34 UTC First seen by agentprime
  2. 31 Oct 2026, 14:34 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.