CVE-2026-1299 MEDIUM

CVE-2026-1299: email BytesGenerator header injection due to unquoted newlines

Vendor Python Software Foundation
Product CPython
Weakness CWE-93 · CRLF injection
Published January 23, 2026
Last update March 3, 2026

CVSS base score

6.0/10
Attack vector Network
Attack complexity Low
Privileges required Low
User interaction None
Confidentiality
Integrity

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N

What the vulnerability does

01Description

The email module, specifically the "BytesGenerator" class, didn’t properly quote newlines for email headers when serializing an email message allowing for header injection when an email is serialized. This is only applicable if using "LiteralHeader" writing headers that don't respect email folding rules, the new behavior will reject the incorrectly folded headers in "BytesGenerator".

Key dates

02Disclosure timeline

January 23, 2026 CVE published
March 3, 2026 Record updated