[oss-security][CVE-2026-3276] Potential DoS via quadratic complexity in unicodedata.normalize()

[Alan Coopersmith <alan.coopersmith () oracle com>]

-------- Forwarded Message --------
Subject: 	[Security-announce][CVE-2026-3276] Potential DoS via quadratic 
complexity in unicodedata.normalize()
Date:   Wed, 3 Jun 2026 14:56:33 +0100
From:   Stan Ulbrych via Security-announce <security-announce () python org>
Reply-To:       security-sig () python org
To:     security-announce () python org
CC:     Stan Ulbrych <stanulbrych () gmail com>



There is a MEDIUM severity vulnerability affecting CPython.

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.

Please see the linked CVE ID for the latest information on affected versions:

* https://www.cve.org/CVERecord?id=CVE-2026-3276
* https://github.com/python/cpython/pull/149080

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