CVE-2026-3276: Python Software Foundation CPython · CWE-407
Affects Python Software Foundation CPythonSource CVE Database V5
Not known to be exploited · CVSS 6.3 Medium · fixed in 3.15.0b2 : update Python Software Foundation CPython when convenient.
Data as of 30 Oct 2026, 06:59 UTC
- EPSS
- 0.4% chance of exploitation in 30 days – higher than 41% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- 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 29 Oct 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
|
| Python Software FoundationCPython | Affected
| Fixed in
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| Python Software FoundationCPython | Affected
| Fixed in
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| Python Software FoundationCPython | Affected
| Fixed in
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| Python Software FoundationCPython | Affected
| Fixed in
|
| Python Software FoundationCPython | Affected
| Fixed in
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Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
If you cannot patch yet, avoid processing untrusted or specially crafted Unicode input with unicodedata.normalize() in performance-critical or exposed environments.
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
- mail.python.org/archives/list/security-announce@python.org/thread/PP5HB4K7727OBBM76KA2ILID76K3OZGZ/ (opens in a new tab)
- github.com/python/cpython/pull/149080 (opens in a new tab)
- github.com/python/cpython/issues/149079 (opens in a new tab)
- github.com/python/cpython/commit/6b505d1f41f8f3ea0fe5a4786d3a8fff1875cfc0 (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/90748760d38ca3ac5fc6788a69becab905c95598 (opens in a new tab)
- openwall.com/lists/oss-security/2026/06/03/15 (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)