VulnerabilityAwaiting Analysis
CVE-2026-3276
unicodedata.normalize() can take excessive CPU time when processing specially crafted Unicode input containing long runs of combining characters with alternating Canonical Combining Class values.
MEDIUM 6.3EPSS 0.49%
Does this matter?
Lower severity and a low EPSS score (0.49%). Track it; it rarely justifies an emergency change on its own.
Description
unicodedata.normalize() can take excessive CPU time when processing specially crafted Unicode input containing long runs of combining characters with alternating Canonical Combining Class values. This affects all normalization forms.
- CVSS 4.0
- 6.3 MEDIUMCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
- EPSS
- 0.49% probability · 40th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-407
- Source
- cna@python.org
References
- https://github.com/python/cpython/commit/6b505d1f41f8f3ea0fe5a4786d3a8fff1875cfc0
- https://github.com/python/cpython/commit/90748760d38ca3ac5fc6788a69becab905c95598
- https://github.com/python/cpython/commit/991224b1e8311c85f198f6dd8208bf8cff7fc26f
- https://github.com/python/cpython/commit/ba785b88add96acbf403d65cb157fb2743a33a32
- https://github.com/python/cpython/commit/c5512bd7c1dc28055660565275012766941d3066
- https://github.com/python/cpython/commit/d3ab945af25b28dfe13ac6cb40c124a01b33ce1f
- https://github.com/python/cpython/commit/db744c0776c1d5dd11aaa70eff2a6993c408bacc
- https://github.com/python/cpython/commit/e322a1857084d521f79f45181b776f62e6acfc2c
- https://github.com/python/cpython/issues/149079
- https://github.com/python/cpython/pull/149080
- https://mail.python.org/archives/list/security-announce@python.org/thread/PP5HB4K7727OBBM76KA2ILID76K3OZGZ/
- http://www.openwall.com/lists/oss-security/2026/06/03/15
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.