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Vulnerability · Published Jan 10, 2026 · Assigned by GitHub_M

CVE-2026-22691pypdf has possible long runtimes for malformed startxref

Low 2.7

In plain English

A low-severity regular-expression denial of service 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 0.4% (higher than 38% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)2.7Low
Exploit odds (30 days)0.4%top 62.2% 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 version 6.6.0, pypdf has possible long runtimes for malformed startxref. An attacker who uses this vulnerability can craft a PDF which leads to possibly long runtimes for invalid startxref entries. When rebuilding the cross-reference table, PDF files with lots of whitespace characters become problematic. Only the non-strict reading mode is affected. Only the non-strict reading mode is affected. This issue has been patched in version 6.6.0.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12pypdfno fix listedDEBIAN-CVE-2026-22691
Debian:13pypdfno fix listedDEBIAN-CVE-2026-22691
Debian:14pypdf6.9.0-1DEBIAN-CVE-2026-22691
Debian:12pypdf2no fix listedDEBIAN-CVE-2026-22691
PyPIpypdf6.6.0GHSA-4f6g-68pf-7vhv
PyPIpypdf6.6.0PYSEC-2026-1828
Ubuntu:24.04:LTSpypdfno fix listedUBUNTU-CVE-2026-22691
Ubuntu:25.10pypdfno fix listedUBUNTU-CVE-2026-22691
Ubuntu:26.04:LTSpypdfno fix listedUBUNTU-CVE-2026-22691
Ubuntu:26.10pypdfno fix listedUBUNTU-CVE-2026-22691
Ubuntu:22.04:LTSpypdf2no fix listedUBUNTU-CVE-2026-22691
Ubuntu:24.04:LTSpypdf2no fix listedUBUNTU-CVE-2026-22691

Affected products (as reported)

VendorProductVersions
py-pdf pypdf < 6.6.0

Weakness: CWE-1333, CWE-400 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U

References