CVE-2025-55197: pypdf's Manipulated FlateDecode streams can exhaust RAM
Impact An attacker who uses this vulnerability 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.
Patches This has been fixed in pypdf==6.0.0.
Workarounds If you cannot upgrade yet, you might want to implement the workaround for pypdf.filters.decompress yourself: https://github.com/py-pdf/pypdf/blob/0dd57738bbdcdb63f0fb43d8a6b3d222b6946595/pypdf/filters.py#L72-L143
References This issue has been reported in #3429 and fixed in #3430.
Other sources
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.
— MITRE
Affected Software
Remediation
Patch Available
Event History
Frequently Asked Questions
What is the severity of CVE-2025-55197?
CVE-2025-55197 is considered a critical vulnerability due to its potential for causing denial of service by exhausting system RAM.
How do I fix CVE-2025-55197?
To fix CVE-2025-55197, update the pypdf package to version 6.0.0 or later.
What types of attacks can exploit CVE-2025-55197?
CVE-2025-55197 can be exploited by attackers through crafted PDF files that leverage FlateDecode filters, leading to RAM exhaustion.
Which software is affected by CVE-2025-55197?
The pypdf package, specifically versions prior to 6.0.0, is affected by CVE-2025-55197.
What are the symptoms of an exploit of CVE-2025-55197?
Symptoms of an exploit include system slowdowns or crashes due to RAM exhaustion when processing malicious PDF files.