What’s Vulnerable › Vulnerabilities

CVE-2026-1502: HTTP client proxy tunnel headers not validated for CR/LF

• 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: 2026-04-10 · updated 2026-10-26
• Weakness: CWE-93

Description

CR/LF bytes were not rejected by HTTP client proxy tunnel headers or host.

Affected products

• Python: before 3.10.21; from 3.11.0 before 3.11.16; from 3.12.0 before 3.12.14; from 3.13.0 before 3.13.14; from 3.14.0a1 before 3.14.5rc1; from 3.15.0a1 before 3.15.0b1 — fixed in 3.10.21, 3.11.16, 3.12.14, 3.13.14, 3.14.5rc1, 3.15.0b1

How to fix

Upgrade to a fixed version: Python 3.10.21, 3.11.16, 3.12.14, 3.13.14. Check the vendor advisory for mitigations.

References

• https://github.com/python/cpython/commit/05ed7ce7ae9e17c23a04085b2539fe6d6d3cef69
• https://github.com/python/cpython/commit/56b7100b04e44ea27989242b176beb8f016b2c53
• https://github.com/python/cpython/commit/58703ec1bdd1eb075e8b01a0c427683ce594dd3e
• https://github.com/python/cpython/commit/9e071c9b28c17f347f81b388a003d4eeb3c7a8dd
• https://github.com/python/cpython/commit/b1cf9016335cb637c5a425032e8274a224f4b2ed
• https://github.com/python/cpython/commit/c00c386faa579ad71196d33408644478488e43ec
• https://github.com/python/cpython/issues/146211
• https://github.com/python/cpython/pull/146212
• https://mail.python.org/archives/list/security-announce@python.org/thread/2IVPAEQWUJBCTQZEJEVTYCIKSMQPGRZ3/
• http://www.openwall.com/lists/oss-security/2026/04/11/4

Get alerted when CVE-2026-1502 or the next vulnerability affects your stack