CRLF injection in Python - CVE-2026-1299
Published: February 13, 2026
Vulnerability identifier: #VU122817
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N/E:U/U:Green
CVE-ID: CVE-2026-1299
CWE-ID: CWE-93
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Python.org
Affected software:
Python
Python
Detailed vulnerability description
The vulnerability allows a remote attacker to inject arbitrary header into email messages.
The vulnerability exists due to insufficient validation of attacker-supplied data in "BytesGenerator" class. A remote attacker can pass specially crafted data to the application containing CR-LF characters and perform a spoofing attack.
How to mitigate CVE-2026-1299
Install updates from vendor's website.
Sources
- https://github.com/python/cpython/commit/052e55e7d44718fe46cbba0ca995cb8fcc359413
- https://github.com/python/cpython/commit/0a925ab591c45d6638f37b5e57796f36fa0e56d8
- https://github.com/python/cpython/commit/7877fe424415bc4a13045e62a90a7277413d8cb9
- https://github.com/python/cpython/commit/842ce19a0c0b58d61591e8f6a708c38db1fb94e4
- https://github.com/python/cpython/commit/8cdf6204f4ae821f32993f8fc6bad0d318f95f36
- https://github.com/python/cpython/issues/144125
- https://github.com/python/cpython/pull/144126
- https://mail.python.org/archives/list/security-announce@python.org/thread/6ZZULGALJTITEAGEXLDJE2C6FORDXPBT/