Improper input validation in Python
CVE-2026-3644
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().
Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.
EPSS exploit prediction
EPSS: 0.007 (49.2th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 49th percentile — 49.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.005 · newest: 0.007 · change: +0.002
Affected products
- Python — versions 3.15.0
- Python Software Foundation Cpython — versions 3.14.0, 0, 3.13.0
Weakness classification (CWE)
References
- mail.python.org/archives/list/security-announce@python.org/thread/H6CADMBCDRFGW… (vendor-advisory, Third Party Advisory)
- github.com/python/cpython/commit/57e88c1cf95e1481b94ae57abe1010469d47a6b4 (Patch, patch)
- github.com/python/cpython/issues/145599 (issue-tracking, Issue Tracking)
- github.com/python/cpython/pull/145600 (Patch, patch)
- github.com/python/cpython/commit/62ceb396fcbe69da1ded3702de586f4072b590dd (Patch, patch)
- github.com/python/cpython/commit/d16ecc6c3626f0e2cc8f08c309c83934e8a979dd (Patch, patch)
- github.com/python/cpython/commit/556aa098e738b127c714866f819b4abe2f7593d8 (patch)
- github.com/python/cpython/commit/dae4b1a21f8df4570e30986affd61bbe4ade4cef (patch)
- github.com/python/cpython/commit/3974092b037f9a3b000fb15b48ea61ce3b25d330 (patch)
Frequently asked questions
- What is CVE-2026-3644?
- CVE-2026-3644 is a high-severity vulnerability in Python, classified under Improper Input Validation. CVSS score: 7.5/10. Published 2026-03-16.
- How severe is CVE-2026-3644?
- High severity. CVSS v3 base score is 7.5 out of 10.