CVE-2026-3276 | THREATINT

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.

PUBLISHED Reserved 2026-02-26 | Published 2026-06-03 | Updated 2026-06-03 | Assigner PSF

MEDIUM: 6.3CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

Problem types

CWE-407

Product status

Default status

unaffected

Any version

affected

Credits

Seokchan Yoon (https://github.com/ch4n3-yoon) reporter

Tim Peters (https://github.com/tim-one) remediation reviewer

Bénédikt Tran (https://github.com/picnixz) remediation reviewer

Serhiy Storchaka (https://github.com/serhiy-storchaka) remediation reviewer

Stan Ulbrych (https://github.com/StanFromIreland) remediation reviewer

Seth Larson (https://github.com/sethmlarson) coordinator

Petr Viktorin (https://github.com/encukou) remediation reviewer

References

mail.python.org/.../thread/PP5HB4K7727OBBM76KA2ILID76K3OZGZ/ vendor-advisory

github.com/python/cpython/pull/149080 patch

github.com/python/cpython/issues/149079 issue-tracking

cve.org (CVE-2026-3276)

nvd.nist.gov (CVE-2026-3276)

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