CVE-2026-0865
HTTP Header Injection via Newlines in Python Headers
Publication date: 2026-01-20
Last updated on: 2026-03-03
Assigner: Python Software Foundation
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| python | cpython | 3.10 |
| python | cpython | 3.11 |
| python | cpython | 3.12 |
| python | cpython | 3.13 |
| python | cpython | 3.14 |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-74 | The product constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
This vulnerability occurs when user-controlled HTTP header names and values include newline characters, which can be exploited to inject additional HTTP headers. This can lead to HTTP header injection attacks.
How can this vulnerability impact me? :
The vulnerability can allow attackers to manipulate HTTP headers, potentially leading to security issues such as response splitting, cache poisoning, or bypassing security controls, which can compromise the integrity and security of web applications.
What immediate steps should I take to mitigate this vulnerability?
To mitigate CVE-2026-0865, you should update your Python environment to a version where the fix has been applied (Python 3.10 through 3.14). The fix enforces validation in the wsgiref.headers.Headers module to reject any control characters, including newline characters, in HTTP header names and values. Applying the official patches or upgrading to a patched Python release will prevent exploitation of this header injection vulnerability. [1, 3]