CVE-2026-82398 pypdf: Inefficient handling of non-whitespace inputs in read_until_whitespace
An attacker can cause denial of service in pypdf by crafting a PDF with long non-whitespace sequences, leading to excessive CPU consumption.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-82398?
CVE-2026-82398 is a medium-severity denial of service vulnerability in Pypdf Project Pypdf, published on 31 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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.
Weakness: CWE-407
Which versions are affected by CVE-2026-82398?
3 open source packages ship an affected version, including pypdf. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
pypdf PyPI | All versions | 6.15.0 |
pypdf PyPI | All versions | 6.15.0 |
pypdf PyPI | All versions | 6.15.0 |
Products include Pypdf Project Pypdf.
How do I fix CVE-2026-82398?
Upgrade pypdf to 6.15.0 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-82398 being exploited?
There is no known exploitation of CVE-2026-82398 in the wild and no public exploit code.
Other vulnerabilities in Pypdf Project Pypdf
- CVE-2026-102993 pypdf: Possible large memory usage when retrieving Roman page labels
- CVE-2026-102994 pypdf: Possible long runtimes/large memory usage when parsing indirect objects
- CVE-2026-102995 pypdf: Possible large memory usage for large /ToUnicode streams (Follow-up 2)
- CVE-2026-102996 pypdf: Possible large memory usage when parsing font data
- CVE-2026-102997 pypdf: Possible long runtimes for partially malformed FlateDecode streams (Follow-up)
Sources
Also known as DEBIAN-CVE-2026-82398, ECHO-c915-e406-2ed8, GHSA-fc8x-2rww-xw9m, MINI-23q6-fmm3-frpw, MINI-59wp-mq5w-qpfr, MINI-74jr-8vc8-jx3c and 14 more.