Potential DoS via quadratic complexity in unicodedata.normalize()
13Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 6.3epss 0.5%
exploitation probability
0.5%top 61% of all CVEs
observed exploitation
nono source reports it
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/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Affected products
Python Software Foundation · CPythonReferences
https://github.com/python/cpython/commit/6b505d1f41f8f3ea0fe5a4786d3a8fff1875cfc0https://github.com/python/cpython/commit/90748760d38ca3ac5fc6788a69becab905c95598https://github.com/python/cpython/commit/991224b1e8311c85f198f6dd8208bf8cff7fc26fhttps://github.com/python/cpython/commit/ba785b88add96acbf403d65cb157fb2743a33a32https://github.com/python/cpython/commit/c5512bd7c1dc28055660565275012766941d3066https://github.com/python/cpython/commit/d3ab945af25b28dfe13ac6cb40c124a01b33ce1fhttps://github.com/python/cpython/commit/db744c0776c1d5dd11aaa70eff2a6993c408bacchttps://github.com/python/cpython/commit/e322a1857084d521f79f45181b776f62e6acfc2chttps://github.com/python/cpython/issues/149079https://github.com/python/cpython/pull/149080https://mail.python.org/archives/list/security-announce@python.org/thread/PP5HB4K7727OBBM76KA2ILID76K3OZGZ/http://www.openwall.com/lists/oss-security/2026/06/03/15