What’s Vulnerable › Vulnerabilities

CVE-2026-0672: Header injection in http.cookies.Morsel

• Severity: medium (CVSS 6.0 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% 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 using http.cookies.Morsel, user-controlled cookie values and parameters can allow injecting HTTP headers into messages. Patch rejects all control characters within cookie names, values, and parameters.

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/62700107418eb2cca3fc88da036a243ea975f172
• https://github.com/python/cpython/commit/712452e6f1d4b9f7f8c4c92ebfcaac1705faa440
• https://github.com/python/cpython/commit/7852d72b653fea0199acf5fc2a84f6f8b84eba8d
• https://github.com/python/cpython/commit/918387e4912d12ffc166c8f2a38df92b6ec756ca
• https://github.com/python/cpython/commit/95746b3a13a985787ef53b977129041971ed7f70
• https://github.com/python/cpython/commit/b1869ff648bbee0717221d09e6deff46617f3e85
• https://github.com/python/cpython/issues/143919
• https://github.com/python/cpython/pull/143920
• https://mail.python.org/archives/list/security-announce@python.org/thread/6VFLQQEIX673KXKFUZXCUNE5AZOGZ45M/

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