Potential DoS via quadratic complexity in unicodedata.normalize()
Summary
| CVE | CVE-2026-3276 |
|---|---|
| State | PUBLISHED |
| Assigner | PSF |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-06-03 16:16:29 UTC |
| Updated | 2026-07-22 19:10:00 UTC |
| 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. |
Risk And Classification
Primary CVSS: v4.0 6.3 MEDIUM from [email protected]
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: 0.004920000 probability, percentile 0.393400000 (date 2026-07-22)
Problem Types: CWE-407 | CWE-407 CWE-407
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 4.0 | [email protected] | Secondary | 6.3 | MEDIUM | 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/C... |
| 4.0 | CNA | CVSS | 6.3 | MEDIUM | 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 |
CVSS v4.0 Breakdown
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
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Python Software Foundation | CPython | affected 3.13.14 python | Not specified |
| CNA | Python Software Foundation | CPython | affected 3.14.0 3.14.6 python | Not specified |
| CNA | Python Software Foundation | CPython | affected 3.15.0a1 3.15.0b2 python | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| github.com/python/cpython/commit/ba785b88add96acbf403d65cb157fb2743a33a32 | [email protected] | github.com | |
| github.com/python/cpython/commit/991224b1e8311c85f198f6dd8208bf8cff7fc26f | [email protected] | github.com | |
| mail.python.org/archives/list/[email protected]/thread/PP5HB4K7727... | [email protected] | mail.python.org | |
| github.com/python/cpython/commit/6b505d1f41f8f3ea0fe5a4786d3a8fff1875cfc0 | [email protected] | github.com | |
| github.com/python/cpython/pull/149080 | [email protected] | github.com | |
| www.openwall.com/lists/oss-security/2026/06/03/15 | af854a3a-2127-422b-91ae-364da2661108 | www.openwall.com | |
| github.com/python/cpython/issues/149079 | [email protected] | github.com | |
| github.com/python/cpython/commit/c5512bd7c1dc28055660565275012766941d3066 | [email protected] | github.com | |
| github.com/python/cpython/commit/90748760d38ca3ac5fc6788a69becab905c95598 | [email protected] | github.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Seokchan Yoon (https://github.com/ch4n3-yoon) (en)
CNA: Tim Peters (https://github.com/tim-one) (en)
CNA: Bénédikt Tran (https://github.com/picnixz) (en)
CNA: Serhiy Storchaka (https://github.com/serhiy-storchaka) (en)
CNA: Stan Ulbrych (https://github.com/StanFromIreland) (en)
CNA: Seth Larson (https://github.com/sethmlarson) (en)
CNA: Petr Viktorin (https://github.com/encukou) (en)