Medium severity · published Aug 31, 2026
CVE-2026-82398
pypdf: Inefficient handling of non-whitespace inputs in read_until_whitespace
5.3
CVSS
0.5%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
Low
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 44% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
PY
pypdf · py-pdf
< 6.15.0 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-82398
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-82398
Patch
https://github.com/py-pdf/pypdf/commit/4959848e057e37c218dccad7465259210923faaa
Patch
https://github.com/py-pdf/pypdf/pull/3947
Release Notes
https://github.com/py-pdf/pypdf/releases/tag/6.15.0
Patch
https://github.com/py-pdf/pypdf/security/advisories/GHSA-fc8x-2rww-xw9m
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