unicodedata.normalize() can take excessive CPU time when processing specially crafted Unicode input containing long
Source GCVE Database
Not known to be exploited · CVSS 6.3 Medium · fixed in 3.15.0b2 : update CPython when convenient.
Data as of 10 Nov 2026, 16:36 UTC
Thin evidence
One scorer or none| CNA (PSF) | CVSS 4.0 | 6.3 |
|---|
- Patch
- Available – fixed in 3.15.0b2, 3.14.6, 3.13.14 +4
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:NExploitation evidence
Disclosed: evidence found.
CVE published 3 Jun 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 10 Nov 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| Python Software FoundationCPython | Affected
| Fixed in
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| Python Software FoundationCPython | Affected
| Fixed in
|
| Python Software FoundationCPython | Affected
| Fixed in
|
| Python Software FoundationCPython | Affected
| Fixed in
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| Python Software FoundationCPython | Affected
| Fixed in
|
| Python Software FoundationCPython | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
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.
References
- nvd.nist.gov/vuln/detail/CVE-2026-3276 (opens in a new tab)
- github.com/python/cpython/issues/149079 (opens in a new tab)
- github.com/python/cpython/pull/149080 (opens in a new tab)
- github.com/python/cpython/commit/6b505d1f41f8f3ea0fe5a4786d3a8fff1875cfc0 (opens in a new tab)
- github.com/python/cpython/commit/90748760d38ca3ac5fc6788a69becab905c95598 (opens in a new tab)
- github.com/python/cpython/commit/991224b1e8311c85f198f6dd8208bf8cff7fc26f (opens in a new tab)
- github.com/python/cpython/commit/ba785b88add96acbf403d65cb157fb2743a33a32 (opens in a new tab)
- github.com/python/cpython/commit/c5512bd7c1dc28055660565275012766941d3066 (opens in a new tab)
- github.com/python/cpython/commit/d3ab945af25b28dfe13ac6cb40c124a01b33ce1f (opens in a new tab)
- github.com/python/cpython/commit/db744c0776c1d5dd11aaa70eff2a6993c408bacc (opens in a new tab)
- github.com/python/cpython/commit/e322a1857084d521f79f45181b776f62e6acfc2c (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-457936.html (opens in a new tab)
- mail.python.org/archives/list/security-announce@python.org/thread/PP5HB4K7727OBBM76KA2ILID76K3OZGZ (opens in a new tab)
- openwall.com/lists/oss-security/2026/06/03/15 (opens in a new tab)