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CVE-2026-6879— Quadratic Behavior in xml.etree.ElementPath Index Predicates

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.

Python Software Foundation CPython是Python Software Foundation基金会的编程语言解释器。 Python Software Foundation CPython 3.15.0之前版本存在安全漏洞，该漏洞源于使用XPath索引谓词时Element.findall()和Element.iterfind()表现出O(n^2)时间复杂度，可能导致CPU消耗。

CVSS 2.0 · Low EPSS 0.37% · P28

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< 3.13.15 affected
3.14.0< 3.14.7 affected
3.15.0a1< 3.15.0rc1 affected
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I. Basic Information for CVE-2026-6879

Vulnerability Information
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Vulnerability Title
Quadratic Behavior in xml.etree.ElementPath Index Predicates
Source: CVE Program / CVE List V5
Vulnerability Description
`Element.findall()` and fully-consumed `Element.iterfind()` exhibit `O(n^2)` time complexity when using XPath index predicates (e.g. `[1]`, `[last()]`, `[last()-N]`) on XML documents with many same-tag siblings. `Element.find()` is only affected when the first match is near the end  of the sibling list, such as with `[last()]` or `[last()-N]`;  `.//item[1]` short-circuits after the first match.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Python Software Foundation CPython 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Python Software Foundation CPython是Python Software Foundation基金会的编程语言解释器。 Python Software Foundation CPython 3.15.0之前版本存在安全漏洞，该漏洞源于使用XPath索引谓词时Element.findall()和Element.iterfind()表现出O(n^2)时间复杂度，可能导致CPU消耗。
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-2026-6879

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III. Intelligence Information for CVE-2026-6879

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Patches & Fixes for CVE-2026-6879 (9)

Vendor Advisories for CVE-2026-6879 (1)

IV. Related Vulnerabilities

Same product: CPython
Same vendor: Python Software Foundation

V. Comments for CVE-2026-6879

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