CVE-2026-27888 pypdf: Manipulated FlateDecode XFA streams can exhaust RAM
Attackers can exhaust RAM by crafting PDFs with manipulated FlateDecode XFA streams, requiring access to the xfa property.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-27888?
CVE-2026-27888 is a medium-severity denial of service vulnerability in Pypdf Project Pypdf, published on 26 Feb 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 6.7.3, an attacker who uses this vulnerability can craft a PDF which leads to the RAM being exhausted. This requires accessing the `xfa` property of a reader or writer and the corresponding stream being compressed using `/FlateDecode`. This has been fixed in pypdf 6.7.3. As a workaround, apply the patch manually.
Weakness: CWE-400
Which versions are affected by CVE-2026-27888?
3 open source packages ship an affected version, including pypdf. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
pypdf PyPI | All versions | 6.7.3 |
pypdf PyPI | All versions | 6.7.3 |
pypdf PyPI | All versions | 6.7.3 |
Products include Pypdf Project Pypdf.
How do I fix CVE-2026-27888?
Upgrade pypdf to 6.7.3 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-2026-27888 being exploited?
There is no known exploitation of CVE-2026-27888 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-2026-27888, GHSA-x7hp-r3qg-r3cj, PYSEC-2026-3027, ROOT-APP-PYPI-CVE-2026-27888, UBUNTU-CVE-2026-27888.