CVE-2026-1299mediumCWE-93

CVE-2026-1299: medium-severity vulnerability in Python Software Foundation CPython

email BytesGenerator header injection due to unquoted newlines

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13Vexday Risk Score

No sign of exploitation. No public exploitation artifact known so far.

ssvc Trackcvss 6epss 0.6%
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".
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
Affected products
Python Software Foundation · CPython
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