CVE-2026-27628 pypdf has a possible infinite loop when loading circular /Prev entries in cross-reference streams
An attacker can cause a denial of service via infinite loop by crafting a PDF with circular cross-reference entries, affecting applications using pypdf.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-27628?
CVE-2026-27628 is a low-severity denial of service vulnerability in Pypdf Project Pypdf, published on 25 Feb 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
pypdf is a free and open-source pure-python PDF library. Prior to 6.7.2, an attacker who uses this vulnerability can craft a PDF which leads to an infinite loop. This requires reading the file. This has been fixed in pypdf 6.7.2. As a workaround, one may apply the patch manually.
Weakness: CWE-835
Which versions are affected by CVE-2026-27628?
3 open source packages ship an affected version, including pypdf. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
pypdf PyPI | All versions | 6.7.2 |
pypdf PyPI | All versions | 6.7.2 |
pypdf PyPI | All versions | 6.7.2 |
Products include Pypdf Project Pypdf.
How do I fix CVE-2026-27628?
Upgrade pypdf to 6.7.2 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-2026-27628 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-27628 exists.
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 CLSA-2026-1778460294, DEBIAN-CVE-2026-27628, GHSA-2rw7-x74f-jg35, PYSEC-2026-3005, ROOT-APP-PYPI-CVE-2026-27628, UBUNTU-CVE-2026-27628.