PSF-2026-1

UNKNOWN

When folding a long comment in an email header containing exclusively unfoldable characters, the parenthesis would not be preserved. This could be used for injecting headers into email messages where

Published Jan 20, 2026

Modified 1 weeks ago

Fix available

Details

When folding a long comment in an email header containing exclusively unfoldable characters, the parenthesis would not be preserved. This could be used for injecting headers into email messages where addresses are user-controlled and not sanitized.

Affected Packages

Python

Windows 10 (1507)Windows 10 (1607) / Server 2016Windows 10 (1809) / Server 2019Windows 10 (1903)Windows 10 (1909)

Fixed in:

3.10.203.11.153.12.133.13.123.14.33.15.0a6

References

FIX

https://github.com/python/cpython/commit/003b8315669b9f08b1010a49071f73f15f818094

FIX

https://github.com/python/cpython/commit/17d1490aa97bd6b98a42b1a9b324ead84e7fd8a2

FIX

https://github.com/python/cpython/commit/61614a5e5056e4f61ced65008d4576f3df34acb6