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Vulnerability · Published Sep 1, 2026 · Assigned by GitHub_M

CVE-2026-84309pypdf: Possible infinite loop for TreeObject.insert_child

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 8% 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 91.7% 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 6.16.0, an attacker can craft a PDF whose cyclic tree structure causes pypdf/generic/_data_structures.py TreeObject.insert_child to follow /Next links indefinitely when a writing code path inserts a child, producing an infinite loop. This issue is fixed in version 6.16.0.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12pypdfno fix listedDEBIAN-CVE-2026-84309
Debian:13pypdfno fix listedDEBIAN-CVE-2026-84309
Debian:14pypdf6.19.0-1DEBIAN-CVE-2026-84309
Debian:12pypdf2no fix listedDEBIAN-CVE-2026-84309
PyPIpypdf6.16.0PYSEC-2026-3913
PyPIpypdf6.16.0GHSA-jp53-mhqp-8xcg
Ubuntu:24.04:LTSpypdfno fix listedUBUNTU-CVE-2026-84309
Ubuntu:26.04:LTSpypdfno fix listedUBUNTU-CVE-2026-84309
Ubuntu:26.10pypdfno fix listedUBUNTU-CVE-2026-84309

Affected products (as reported)

VendorProductVersions
py-pdf pypdf < 6.16.0

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