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CVE-2026-3276— Potential DoS via quadratic complexity in unicodedata.normalize()

Quick assessment

Affected
Python Software Foundation CPython
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

CPython是Python基金会的一个用C语言实现的Python解释器。 CPython存在安全漏洞，该漏洞源于处理特制Unicode输入时CPU消耗过高，可能导致拒绝服务。

CVSS 6.3 · Medium EPSS 0.71% · P52

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking

Affected Version Matrix 6

VendorProduct Version RangeStatus
Python Software Foundation CPython < 3.10.21 affected
3.11.0< 3.11.16 affected
3.12.0< 3.12.14 affected
3.13.0< 3.13.14 affected
3.14.0< 3.14.6 affected
3.15.0a1< 3.15.0b2 affected
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I. Basic Information for CVE-2026-3276

Vulnerability Information
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Vulnerability Title
Potential DoS via quadratic complexity in unicodedata.normalize()
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
算法复杂性
Source: CVE Program / CVE List V5
Vulnerability Title
CPython 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
CPython是Python基金会的一个用C语言实现的Python解释器。 CPython存在安全漏洞，该漏洞源于处理特制Unicode输入时CPU消耗过高，可能导致拒绝服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Python Software Foundation CPython 0 ~ 3.10.21 -

II. Public POCs for CVE-2026-3276

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III. Intelligence Information for CVE-2026-3276

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Patches & Fixes for CVE-2026-3276 (9)

Mailing List Discussions for CVE-2026-3276 (1)

IV. Related Vulnerabilities

Same product: CPython
Same vendor: Python Software Foundation
Same weakness: CWE-407

V. Comments for CVE-2026-3276

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