# CVE-2026-3644: Incomplete control character validation in http.cookies

> Incomplete control character validation in Python's http.cookies module allows bypassing input checks, potentially leading to header injection or parsing issues.

- **Severity:** Medium 6.0 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 16 Mar 2026
- **Updated:** 13 Aug 2026
- **Also known as:** ALPINE-CVE-2026-3644, AZL-109704, AZL-80055, BELL-CVE-2026-3644, DEBIAN-CVE-2026-3644, ECHO-6a47-d40a-2c76, GHSA-vf33-88pf-hwp3, MINI-f36w-g3gx-qm83, MINI-g56q-jvcw-gqw6, MINI-v4jw-865m-9wr6, MINI-x38x-p8r4-rhf5, MINI-xwh9-pj6q-58x2, PSF-2026-11, ROOT-OS-ALPINE-320-CVE-2026-3644, ROOT-OS-DEBIAN-12-CVE-2026-3644, UBUNTU-CVE-2026-3644

## What is CVE-2026-3644?

CVE-2026-3644 is a medium-severity vulnerability in Python Python, published on 16 Mar 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

The fix for CVE-2026-0672, which rejected control characters in http.cookies.Morsel, was incomplete. The Morsel.update(), |= operator, and unpickling paths were not patched, allowing control characters to bypass input validation. Additionally, BaseCookie.js_output() lacked the output validation applied to BaseCookie.output().

Weakness: CWE-20 (Improper Input Validation), CWE-116 (Improper Encoding or Escaping of Output)

## Which versions are affected by CVE-2026-3644?

It affects 1 product.


Products: Python Python.

## How do I fix CVE-2026-3644?

Apply the vendor's patch.

## Is CVE-2026-3644 being exploited?

There is no known exploitation of CVE-2026-3644 in the wild and no public exploit code.

## Other vulnerabilities in Python Python

- [CVE-2008-5031](https://insights.sbomify.com/CVE-2008-5031/): Integer overflow in n/a (critical 10.0)
- [CVE-2014-4650](https://insights.sbomify.com/CVE-2014-4650/): Path traversal in n/a (critical 9.8)
- [CVE-2016-5636](https://insights.sbomify.com/CVE-2016-5636/): Integer overflow in n/a (critical 9.8)
- [CVE-2007-4559](https://insights.sbomify.com/CVE-2007-4559/): Path traversal in n/a (critical 9.8)
- [CVE-2017-17522](https://insights.sbomify.com/CVE-2017-17522/): Command injection in n/a (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-3644 and fix it if it is affected.

What it is: CVE-2026-3644 is a medium-severity vulnerability in Python Python, published on 16 Mar 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-3644 in the wild and no public exploit code.

Affected product: Python Python. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-3644/ (Markdown: https://insights.sbomify.com/CVE-2026-3644/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-3644
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-3644
- OSV: https://osv.dev/vulnerability/CVE-2026-3644

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-3644/
Summaries are generated and may contain mistakes; the official description above is the record.