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CVE-2026-3276

Potential DoS via quadratic complexity in unicodedata.normalize()

MEDIUM
6.3
CVSS Score
Published: June 3, 2026 at 02:29 PM UTC
Updated: August 13, 2026 at 01:16 AM UTC
1 product affected across 1 vendorPython

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Severity
MEDIUM6.3
Exploit prediction
EPSS 0.5%
SSVC
No known exploit

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

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Python· Python
60%
v < 3.10.213.11.0 ≤ v < 3.11.163.12.0 ≤ v < 3.12.143.13.0 ≤ v < 3.13.143.14.0 ≤ v < 3.14.63.15.0a1 ≤ v < 3.15.0b23.11.03.12.03.13.03.14.03.15.0a1
Affected range stops below 3.10.21, so it looks safe — our inference, not a vendor statement
Affected range stops below 3.11.16, so it looks safe — our inference, not a vendor statement
Affected range stops below 3.12.14, so it looks safe — our inference, not a vendor statement
Affected range stops below 3.13.14, so it looks safe — our inference, not a vendor statement
Affected range stops below 3.14.6, so it looks safe — our inference, not a vendor statement
Affected range stops below 3.15.0b2, so it looks safe — our inference, not a vendor statement

References (12)

Vendor Advisory
Source: cverecord
https://mail.python.org/archives/list/[email protected]/thread/PP5HB4K7727OBBM76KA2ILID76K3OZGZ/
Patch
Source: cverecord
https://github.com/python/cpython/pull/149080
Issue Tracking
Source: cverecord
https://github.com/python/cpython/issues/149079
Source: af854a3a-2127-422b-91ae-364da2661108
http://www.openwall.com/lists/oss-security/2026/06/03/15
Patch
Source: cverecord
https://github.com/python/cpython/commit/6b505d1f41f8f3ea0fe5a4786d3a8fff1875cfc0
Patch
Source: cverecord
https://github.com/python/cpython/commit/991224b1e8311c85f198f6dd8208bf8cff7fc26f
Patch
Source: cverecord
https://github.com/python/cpython/commit/ba785b88add96acbf403d65cb157fb2743a33a32
Patch
Source: cverecord
https://github.com/python/cpython/commit/c5512bd7c1dc28055660565275012766941d3066

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

6.3MEDIUMPSF
Vector?

Quick Info

StatusAWAITING ANALYSIS
CWE
CWE-407

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