What’s Vulnerable › Vulnerabilities

CVE-2025-11468: Folding email comments of unfoldable characters doesn't preserve parenthesis

• Severity: medium (CVSS 5.7 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-01-20 · updated 2026-06-17
• Weakness: CWE-93

Description

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 products

• Python: before 3.10.20; from 3.11.0 before 3.11.15; from 3.12.0 before 3.12.13; from 3.13.0 before 3.13.12; from 3.14.0 before 3.14.3; from 3.15.0a1 before 3.15.0a6 — fixed in 3.10.20, 3.11.15, 3.12.13, 3.13.12, 3.14.3, 3.15.0a6

How to fix

Upgrade to a fixed version: Python 3.10.20, 3.11.15, 3.12.13, 3.13.12. Check the vendor advisory for mitigations.

References

• https://github.com/python/cpython/commit/003b8315669b9f08b1010a49071f73f15f818094
• https://github.com/python/cpython/commit/17d1490aa97bd6b98a42b1a9b324ead84e7fd8a2
• https://github.com/python/cpython/commit/61614a5e5056e4f61ced65008d4576f3df34acb6
• https://github.com/python/cpython/commit/a76e4cd62dd68e7cbe86e37e6ed988495a646b66
• https://github.com/python/cpython/commit/e9970f077240c7c670e8a6fc6662f2b30d3b6ad0
• https://github.com/python/cpython/commit/f738386838021c762efea6c9802c82de65e87796
• https://github.com/python/cpython/issues/143935
• https://github.com/python/cpython/pull/143936
• https://mail.python.org/archives/list/security-announce@python.org/thread/FELSEOLBI2QR6YLG6Q7VYF7FWSGQTKLI/

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