Python CPython O(n^2) XPath index in Element.findall()/iterfind (pre-3.15)
CVE-2026-6879 Published on July 28, 2026
Quadratic Behavior in xml.etree.ElementPath Index Predicates
`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.
Vulnerability Analysis
CVE-2026-6879 can be exploited with network access. This vulnerability is consided to have a high level of attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity and availability.
Weakness Type
Inefficient Algorithmic Complexity
An 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.
Products Associated with CVE-2026-6879
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Affected Versions
Python Software Foundation CPython:- Before 3.15.0 is affected.