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.

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements Present

User Interaction None

Vulnerable System Confidentiality Impact None

Vulnerable System Integrity Impact None

Vulnerable System Availability Impact Low

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

No CVSS v3.1

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Exploitation none

Automatable no

Technical Impact partial

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
Python Software Foundation CPython unaffected
Version Status Constraints
0 affected —

No data.

No data.

OpenCVE Enrichment is a feature of OpenCVE that uses AI to automatically link vendors and products to CVEs. Learn more on GitHub.

No data.

Project Subscriptions

No data.

Advisories

No advisories yet.

Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://github.com/python/cpython/issues/149079 cve-icon cve-icon
https://github.com/python/cpython/pull/149080 cve-icon cve-icon
https://mail.python.org/archives/list/security-announce@python.org/thread/PP5HB4K7727OBBM76KA2ILID76K3OZGZ/ cve-icon cve-icon
History

Wed, 03 Jun 2026 18:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Wed, 03 Jun 2026 16:00:00 +0000

Type Values Removed Values Added
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.
Title Potential DoS via quadratic complexity in unicodedata.normalize()
Weaknesses CWE-407
References
Metrics cvssV4_0

{'score': 6.3, 'vector': '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'}

Projects

Sign in to view the affected projects.

cve-icon MITRE

Status: PUBLISHED

Assigner: PSF

Published:

Updated: 2026-06-03T17:27:19.179Z

Reserved: 2026-02-26T15:19:46.862Z

Link: CVE-2026-3276

cve-icon Vulnrichment

Updated: 2026-06-03T17:27:13.504Z

cve-icon NVD

Status : Received

Published: 2026-06-03T16:16:29.253

Modified: 2026-06-03T16:16:29.253

Link: CVE-2026-3276

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-06-03T18:00:07Z

Weaknesses