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6.3 Medium

CVE-2026-3276 unicodedata.normalize() can take excessive CPU time when processing specially crafted Unicode input containing long runs…

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.

Affected products and versions

Product Affected versions Fixed in
CPython 3.15 3.15.0a1 → < 3.15.0b2 3.15.0b2
CPython 3.14 3.14.0 → < 3.14.6 3.14.6
CPython 3.13 3.13.0 → < 3.13.14 3.13.14
CPython 3.12 3.12.0 → < 3.12.14 3.12.14
CPython 3.11 3.11.0 → < 3.11.16 3.11.16
CPython 3.10 earliest → < 3.10.21 3.10.21

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