CVE-2026-6879: python software foundation cpython Inefficient Algorithmic Complexity

Vulnerability summary

CVE-2026-6879 is a low (CVSS 2.0) Inefficient Algorithmic Complexity vulnerability in python software foundation cpython. EPSS estimates a 0.37% chance of exploitation in the next 30 days, higher than 29.3% of scored vulnerabilities.

Timeline

1. 28-07-2026
   PublishedVulnerability first disclosed.
2. 13-08-2026
   Last modifiedVulnerability information updated.

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.

• CWE-407Inefficient Algorithmic ComplexityAn algorithm in a product has an inefficient worst-case computational complexity that may be detrimental to system performance and can be triggered by an attacker, typically using crafted manipulations that ensure that the worst case is being reached.