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Vulnerability · Published May 28, 2026 · Assigned by GitHub_M

CVE-2026-48156pypdf: Possible long runtimes for zero-only width values in cross-reference streams

Medium 5.1

In plain English

A medium-severity security flaw 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 0.1% (higher than 2% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)5.1Medium
Exploit odds (30 days)0.1%top 97.9% 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 6.12.0, an attacker who uses this vulnerability can craft a PDF which leads to long runtimes. This requires cross-reference streams with /W [0 0 0] values and large /Size values. This vulnerability is fixed in 6.12.0.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12pypdfno fix listedDEBIAN-CVE-2026-48156
Debian:13pypdfno fix listedDEBIAN-CVE-2026-48156
Debian:14pypdf6.19.0-1DEBIAN-CVE-2026-48156
Debian:12pypdf2no fix listedDEBIAN-CVE-2026-48156
PyPIpypdf6.12.0GHSA-248m-82v9-q6g6
PyPIpypdf6.12.0PYSEC-2026-3004
Ubuntu:24.04:LTSpypdfno fix listedUBUNTU-CVE-2026-48156
Ubuntu:25.10pypdfno fix listedUBUNTU-CVE-2026-48156
Ubuntu:26.04:LTSpypdfno fix listedUBUNTU-CVE-2026-48156
Ubuntu:26.10pypdfno fix listedUBUNTU-CVE-2026-48156
Ubuntu:22.04:LTSpypdf2no fix listedUBUNTU-CVE-2026-48156
Ubuntu:24.04:LTSpypdf2no fix listedUBUNTU-CVE-2026-48156

Affected products (as reported)

VendorProductVersions
py-pdf pypdf < 6.12.0

Weakness: CWE-834 · Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

References