CVE-2026-6879

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.

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Weakness Type (CWE)

CWE-407 CWE-407

References

Other References

https://github.com/python/cpython/commit/2ffab083782968a4d732738f4f1dff6bbd69d2b0 https://github.com/python/cpython/issues/152674 https://github.com/python/cpython/pull/152676 https://mail.python.org/archives/list/[email protected]/thread/7YMZ6DDZVR26TJJBVO3RDNBAVGHNYAKR/

Frequently Asked Questions

What is CVE-2026-6879? +

`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.

How do I check if I'm vulnerable to CVE-2026-6879? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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