CVE-2026-0865
Unknown Unknown - Not Provided
HTTP Header Injection via Newlines in Python Headers

Publication date: 2026-01-20

Last updated on: 2026-03-03

Assigner: Python Software Foundation

Description
User-controlled header names and values containing newlines can allow injecting HTTP headers.
CVSS Scores
EPSS Scores
Probability:
Percentile:
Meta Information
Published
2026-01-20
Last Modified
2026-03-03
Generated
2026-06-16
AI Q&A
2026-01-21
EPSS Evaluated
2026-06-15
NVD
CVE-2026-0865
Affected Vendors & Products
Showing 5 associated CPEs
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
CWE Icon
KEV
KEV Icon
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 Quick Actions
Instant insights powered by AI
Executive Summary

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.

Impact Analysis

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.

Mitigation Strategies

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]

Chat Assistant
Ask questions about this CVE
Hi! I’m here to help you understand CVE-2026-0865. Ask me anything about the vulnerability, its impact, or mitigation strategies.
0/70
EPSS Chart