CVE-2025-55197 pypdf's Manipulated FlateDecode streams can exhaust RAM
Attackers can exhaust RAM by crafting malicious PDFs with specific FlateDecode filters, causing denial of service in applications using pypdf.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-55197?
CVE-2025-55197 is a medium-severity denial of service vulnerability in Pypdf Project Pypdf, published on 13 Aug 2025. 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 version 6.0.0, an attacker can craft a PDF which leads to the RAM being exhausted. This requires just reading the file if a series of FlateDecode filters is used on a malicious cross-reference stream. Other content streams are affected on explicit access. This issue has been fixed in 6.0.0. If an update is not possible, a workaround involves including the fixed code from pypdf.filters.decompress into the existing filters file.
Which versions are affected by CVE-2025-55197?
3 open source packages ship an affected version, including pypdf. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
pypdf PyPI | All versions | 6.0.0 |
pypdf PyPI | All versions | 6.0.0 |
pypdf PyPI | All versions | 6.0.0 |
Linux distribution packages (1)
python-pypdf openSUSE:Tumbleweed | All versions | 6.0.0-1.1 |
Products include Pypdf Project Pypdf.
How do I fix CVE-2025-55197?
Upgrade pypdf to 6.0.0 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-2025-55197 being exploited?
There is no known exploitation of CVE-2025-55197 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 CLSA-2025-1759968741, DEBIAN-CVE-2025-55197, GHSA-7hfw-26vp-jp8m, PYSEC-2026-1830, UBUNTU-CVE-2025-55197, openSUSE-SU-2025:15439-1.