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Vulnerability · Published Aug 31, 2026 · Assigned by GitHub_M

CVE-2026-82398pypdf: Inefficient handling of non-whitespace inputs in read_until_whitespace

Medium 6.9

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 0.5% (higher than 45% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)6.9Medium
Exploit odds (30 days)0.5%top 55.4% 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 6.15.0, an attacker can craft a PDF that causes long runtimes when the pypdf/_utils.py function read_until_whitespace reads a stream containing a long run of bytes without whitespace. The function repeatedly performs immutable bytes concatenation in a one-byte loop, causing quadratic processing cost for the long non-whitespace input. This issue is fixed in version 6.15.0.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12pypdfno fix listedDEBIAN-CVE-2026-82398
Debian:13pypdfno fix listedDEBIAN-CVE-2026-82398
Debian:14pypdf6.19.0-1DEBIAN-CVE-2026-82398
Debian:12pypdf2no fix listedDEBIAN-CVE-2026-82398
PyPIpypdf6.15.0GHSA-fc8x-2rww-xw9m
PyPIpypdf6.15.0PYSEC-2026-3912
Ubuntu:24.04:LTSpypdfno fix listedUBUNTU-CVE-2026-82398
Ubuntu:26.04:LTSpypdfno fix listedUBUNTU-CVE-2026-82398
Ubuntu:26.10pypdfno fix listedUBUNTU-CVE-2026-82398
Ubuntu:22.04:LTSpypdf2no fix listedUBUNTU-CVE-2026-82398
Ubuntu:24.04:LTSpypdf2no fix listedUBUNTU-CVE-2026-82398

Affected products (as reported)

VendorProductVersions
py-pdf pypdf < 6.15.0

Weakness: CWE-407 · 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

References