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Vulnerability · Published Jun 22, 2026 · Assigned by GitHub_M

CVE-2026-54651pypdf: Possible infinite loop when processing threads/articles in writer

Medium 6.9

In plain English

A medium-severity infinite loop 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 0.2% (higher than 5% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)6.9Medium
Exploit odds (30 days)0.2%top 95.0% 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 6.13.1, an attacker who uses this vulnerability can craft a PDF which leads to an infinite loop. This requires merging a file with threads/articles into a writer. This vulnerability is fixed in 6.13.1.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12pypdfno fix listedDEBIAN-CVE-2026-54651
Debian:13pypdfno fix listedDEBIAN-CVE-2026-54651
Debian:14pypdf6.19.0-1DEBIAN-CVE-2026-54651
Debian:12pypdf2no fix listedDEBIAN-CVE-2026-54651
PyPIpypdf6.13.1GHSA-g9xf-7f8q-9mcj
PyPIpypdf6.13.1PYSEC-2026-3018
Ubuntu:24.04:LTSpypdfno fix listedUBUNTU-CVE-2026-54651
Ubuntu:25.10pypdfno fix listedUBUNTU-CVE-2026-54651
Ubuntu:26.04:LTSpypdfno fix listedUBUNTU-CVE-2026-54651
Ubuntu:26.10pypdfno fix listedUBUNTU-CVE-2026-54651
Ubuntu:22.04:LTSpypdf2no fix listedUBUNTU-CVE-2026-54651
Ubuntu:24.04:LTSpypdf2no fix listedUBUNTU-CVE-2026-54651

Affected products (as reported)

VendorProductVersions
py-pdf pypdf < 6.13.1

Weakness: CWE-835 · Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

References