CVE-2026-3276

Summary

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 Software

Weaknesses

• CWE-407: CWE-407

ADP Enrichment

CISA ADP Vulnrichment

• SSVC:
• Exploitation: none
  • Automatable: no
  • Technical Impact: partial

CVE Program Container

Additional References

• http://www.openwall.com/lists/oss-security/2026/06/03/15

References

• https://mail.python.org/archives/list/security-announce@python.org/thread/PP5HB4K7727OBBM76KA2ILID76K3OZGZ/
• https://github.com/python/cpython/pull/149080
• https://github.com/python/cpython/issues/149079
• https://github.com/python/cpython/commit/6b505d1f41f8f3ea0fe5a4786d3a8fff1875cfc0
• https://github.com/python/cpython/commit/991224b1e8311c85f198f6dd8208bf8cff7fc26f
• https://github.com/python/cpython/commit/ba785b88add96acbf403d65cb157fb2743a33a32
• https://github.com/python/cpython/commit/c5512bd7c1dc28055660565275012766941d3066
• https://github.com/python/cpython/commit/90748760d38ca3ac5fc6788a69becab905c95598

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