CVE-2026-27026
Denial of Service via Malformed /FlateDecode in pypdf
Publication date: 2026-02-20
Last updated on: 2026-02-24
Assigner: GitHub, Inc.
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| pypdf_project | pypdf | to 6.7.1 (exc) |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-770 | The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
This vulnerability exists in the pypdf library, a pure-python PDF library. Before version 6.7.1, an attacker could craft a specially malformed PDF containing a /FlateDecode stream that triggers byte-by-byte decompression. This causes the library to experience long runtimes, effectively leading to a denial of service through resource exhaustion.
How can this vulnerability impact me? :
The impact of this vulnerability is that an attacker can cause the pypdf library to consume excessive processing time by providing a malicious PDF. This can lead to performance degradation or denial of service in applications that use pypdf to process PDF files, potentially disrupting normal operations.
How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:
I don't know
How can this vulnerability be detected on my network or system? Can you suggest some commands?
I don't know
What immediate steps should I take to mitigate this vulnerability?
To mitigate this vulnerability, you should upgrade the pypdf library to version 6.7.1 or later, where the issue with malformed /FlateDecode streams causing long runtimes has been fixed.