CVE-2026-1299

NameCVE-2026-1299
DescriptionThe 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".
SourceCVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
pypy3 (PTS)bullseye7.3.5+dfsg-2+deb11u2vulnerable
bullseye (security)7.3.5+dfsg-2+deb11u5vulnerable
bookworm7.3.11+dfsg-2+deb12u3vulnerable
trixie7.3.19+dfsg-2vulnerable
forky, sid7.3.20+dfsg-4vulnerable
python3.11 (PTS)bookworm3.11.2-6+deb12u6vulnerable
bookworm (security)3.11.2-6+deb12u3vulnerable
python3.13 (PTS)trixie3.13.5-2vulnerable
forky, sid3.13.11-1vulnerable
python3.14 (PTS)forky, sid3.14.2-1vulnerable
python3.9 (PTS)bullseye3.9.2-1vulnerable
bullseye (security)3.9.2-1+deb11u4vulnerable

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
pypy3source(unstable)(unfixed)
python3.11source(unstable)(unfixed)
python3.13source(unstable)(unfixed)
python3.14source(unstable)(unfixed)
python3.9source(unstable)(unfixed)

Notes

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/
https://github.com/python/cpython/commit/052e55e7d44718fe46cbba0ca995cb8fcc359413 (main)

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