CVE-2025-66019

pypdf manipulated LZWDecode streams can exhaust RAM

At a glance

Severity: MEDIUM 6.6
EPSS: EPSS 0.39 % · percentile 33 (2026-10-27)
State: PUBLISHED
Published: 2025-11-25
Updated: 2026-01-20
Assigner: GitHub_M
NVD status: Deferred

Description

pypdf is a free and open-source pure-python PDF library. Prior to version 6.4.0, an attacker who uses this vulnerability can craft a PDF which leads to a memory usage of up to 1 GB per stream. This requires parsing the content stream of a page using the LZWDecode filter. This issue has been patched in version 6.4.0.

Scores

Version	Score	Vector	Scored by
CVSS 4.0	MEDIUM 6.6	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	GitHub_M
CVSS 4.0	MEDIUM 6.6	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/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X	NVD · security-advisories@github.com (Secondary)

Weaknesses (CWE)

Advisories

GHSA-m449-cwjh-6pw7 — pypdf's LZWDecode streams be manipulated to exhaust RAM
PYSEC-2026-1832 — pypdf's LZWDecode streams be manipulated to exhaust RAM

European references

ENISA EUVD · EUVD-2025-199017
GCVE · GCVE-0-2025-66019

CERT-FR advisories

CERTFR-2026-AVI-0224 — Multiples vulnérabilités dans les produits IBM · cert.ssi.gouv.fr

Affected products

Product	Versions
py-pdf · pypdf	affected < 6.4.0

References

Sources

Source	Licence
CVE List (CVEProject cvelistV5)	CVE Program Terms of Use
EPSS (FIRST.org)	FIRST — attribution requested
ENISA EUVD	ENISA — reproduction authorised, source acknowledged
CERT-FR (ANSSI)	Licence Ouverte / Etalab 2.0
NVD (NIST) via fkie-cad/nvd-json-data-feeds	Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD