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CVE-2026-3276
Potential DoS via quadratic complexity in unicodedata.normalize()
Medium6.3EPSS 0.49%
- Published
- Updated
- Reserved
- Assigned by
- PSF
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.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| PSFCNA (assigner) | 4.0 | Medium6.3 | 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 |
| NVDNVD · Awaiting Analysis | 4.0 | Medium6.3 | 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
- EPSS (exploitation in 30 days)
- 0.49% · top 58% of all CVEs (6 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
Loading the EPSS history…
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 6.3.
Weakness
Affected products
Python Software Foundation · CPython
- affected < 3.10.21
- affected 3.11.0 – < 3.11.16
- affected 3.12.0 – < 3.12.14
- affected 3.13.0 – < 3.13.14
- affected 3.14.0 – < 3.14.6
- affected 3.15.0a1 – < 3.15.0b2
References (12)
- https://mail.python.org/archives/list/[email protected]/thread/PP5HB4K7727OBBM76KA2ILID76K3OZGZ/ (opens in a new tab)vendor-advisory
- https://github.com/python/cpython/pull/149080 (opens in a new tab)patch
- https://github.com/python/cpython/issues/149079 (opens in a new tab)issue-tracking
- https://github.com/python/cpython/commit/6b505d1f41f8f3ea0fe5a4786d3a8fff1875cfc0 (opens in a new tab)patch
- https://github.com/python/cpython/commit/991224b1e8311c85f198f6dd8208bf8cff7fc26f (opens in a new tab)patch
- https://github.com/python/cpython/commit/ba785b88add96acbf403d65cb157fb2743a33a32 (opens in a new tab)patch
- https://github.com/python/cpython/commit/c5512bd7c1dc28055660565275012766941d3066 (opens in a new tab)patch
- https://github.com/python/cpython/commit/90748760d38ca3ac5fc6788a69becab905c95598 (opens in a new tab)patch
- https://github.com/python/cpython/commit/d3ab945af25b28dfe13ac6cb40c124a01b33ce1f (opens in a new tab)patch
- https://github.com/python/cpython/commit/db744c0776c1d5dd11aaa70eff2a6993c408bacc (opens in a new tab)patch
- https://github.com/python/cpython/commit/e322a1857084d521f79f45181b776f62e6acfc2c (opens in a new tab)patch
- http://www.openwall.com/lists/oss-security/2026/06/03/15 (opens in a new tab)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
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[](https://trackcve.app/cve/CVE-2026-3276)Record last updated .