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Vulnerability · Published Sep 30, 2026 · Assigned by GitHub_M

CVE-2026-102997pypdf: Possible long runtimes for partially malformed FlateDecode streams (Follow-up)

High 8.7

In plain English

A high-severity uncontrolled resource consumption in pypdf from py-pdf. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 28% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)8.7High
Exploit odds (30 days)0.3%top 72.3% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

pypdf is a free and open-source pure-python PDF library. Prior to 6.18.1, a crafted PDF containing a partially malformed /FlateDecode stream with padded data can force pypdf/filters.py to use inefficient byte-by-byte decompression while the earlier recovery counter fails to advance for bytes that successfully decode, causing long runtimes and application unavailability. This is a residual issue after the malformed FlateDecode recovery fix. This issue is fixed in version 6.18.1.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12pypdfno fix listedDEBIAN-CVE-2026-102997
Debian:13pypdfno fix listedDEBIAN-CVE-2026-102997
Debian:14pypdf6.19.0-1DEBIAN-CVE-2026-102997
Debian:12pypdf2no fix listedDEBIAN-CVE-2026-102997
PyPIpypdf6.18.1GHSA-jw7q-gvrg-4vj3
PyPIpypdf6.18.1PYSEC-2026-4156
Ubuntu:24.04:LTSpypdfno fix listedUBUNTU-CVE-2026-102997
Ubuntu:26.04:LTSpypdfno fix listedUBUNTU-CVE-2026-102997
Ubuntu:26.10pypdfno fix listedUBUNTU-CVE-2026-102997
Ubuntu:22.04:LTSpypdf2no fix listedUBUNTU-CVE-2026-102997
Ubuntu:24.04:LTSpypdf2no fix listedUBUNTU-CVE-2026-102997

Affected products (as reported)

VendorProductVersions
py-pdf pypdf < 6.18.1

Weakness: CWE-400, CWE-407 · Vector: 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

References