What is CVE-2026-82398?
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.
The record classifies CVE-2026-82398 under weakness class CWE-407. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 35 days ago.
Severity and exploitation probability
- CVSS v4.0 base score
- 6.9 — Medium (derived from score)
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 - EPSS (FIRST)
- 0.3% probability of exploitation in the next 30 days, higher than 22.2% of all scored CVEs
- CISA KEV
- Not listed in the CISA Known Exploited Vulnerabilities catalog
- Threadlinqs priority
- 4.3/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- Published
- 2026-08-31, last modified 2026-09-01
Is CVE-2026-82398 being exploited?
It currently carries a trending score of 35 in the Threadlinqs vulnerability feed.
Affected products and versions
- py-pdf: pypdf
How to fix CVE-2026-82398
No vendor patch reference has been recorded for CVE-2026-82398 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.
Threat activity tracking CVE-2026-82398
No threat campaign in the Threadlinqs corpus currently references CVE-2026-82398, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.
Sources
Enriched from CVE.org, NVD, FIRST EPSS. Last verified by Threadlinqs on . This product uses the NVD API but is not endorsed or certified by the NVD.