Vulnerability · Published Oct 29, 2026 · Assigned by GitHub_M

CVE-2026-119205pypdf: Possible infinite loop when cloning dictionaries

High 7.1

In plain English

A high-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 13% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)7.1High

Exploit odds (30 days)0.2%top 87.3% 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 6.21.4, pypdf can enter an infinite loop when cloning or duplicating a crafted cyclic DictionaryObject. Clone traversal checked generated destination references rather than the original source references, allowing some source cycles to evade the visited-object check. This issue is fixed in version 6.21.4.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:12	pypdf	no fix listed	DEBIAN-CVE-2026-119205
Debian:13	pypdf	no fix listed	DEBIAN-CVE-2026-119205
Debian:14	pypdf	6.21.4-1	DEBIAN-CVE-2026-119205
Debian:12	pypdf2	no fix listed	DEBIAN-CVE-2026-119205
PyPI	pypdf	6.21.4	GHSA-mfr5-77xh-9j7h
Ubuntu:24.04:LTS	pypdf	no fix listed	UBUNTU-CVE-2026-119205
Ubuntu:26.04:LTS	pypdf	no fix listed	UBUNTU-CVE-2026-119205
Ubuntu:26.10	pypdf	no fix listed	UBUNTU-CVE-2026-119205

Affected products (as reported)

Vendor	Product	Versions
py-pdf	pypdf	< 6.21.4

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

References

https://github.com/py-pdf/pypdf/security/advisories/GHSA-mfr5-77xh-9j7h x_refsource_CONFIRM
https://github.com/py-pdf/pypdf/pull/4288 x_refsource_MISC
https://github.com/py-pdf/pypdf/commit/f176db1a1f7f9af3e472e69a843ef1175653b044 x_refsource_MISC
https://github.com/py-pdf/pypdf/releases/tag/6.21.4 x_refsource_MISC