CVE-2026-6879
CVE-2026-6879 — 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.
Published Updated Sources: cvelistV5, PSF
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.
Exploitation
Unreported
no source claims exploitation
EPSS
0%
chance of exploitation in 30 days
CVSS base
2
LOW
CISA SSVC assessment
Three decision points CISA publishes for the CVEs it assesses · SSVC 2.0.3. A stakeholder decision, not a severity score.
Exploitation
None
none · proof-of-concept · active
Automatable
No
can an attacker script all four kill-chain steps
Technical impact
Partial
partial · total control of the vulnerable component
Affected scope
The catalog records vendors and products as separate lists, not pairs, so which product belongs to which vendor is not something this page can say.
Vendors (1)
Products (1)
Every base score collected
Sources score independently and disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Source |
|---|---|---|---|---|---|
| 2 | CVSS 4.0 | LOW | — | — | cvelistV5 |
Weakness & attack patterns
- CWE-407
Detection
Read off the CVSS vector and the weakness class. Starting points, not rules we have tested.
- Search application, proxy, and WAF logs for requests touching //item[1].
References
10 on the record
- github.com/python/cpython/pull/152676
patch
- github.com/python/cpython/issues/152674
issue-tracking
- mail.python.org/archives/list/[email protected]/thread/7YMZ6DDZVR26TJJBVO3RDNBAVGHNYAKR/
vendor-advisory
- github.com/python/cpython/commit/2ffab083782968a4d732738f4f1dff6bbd69d2b0
patch
- github.com/python/cpython/commit/02c08e6b747ac43d0d866a4ffa916bedf3423f81
patch
- github.com/python/cpython/commit/390337b8ba1658833fdef379e1739c9f9533a8db
patch
- github.com/python/cpython/commit/cb409342a19f25656f62e679f8bac265fe1442c3
patch
- github.com/python/cpython/commit/96510a3758f4a075f43223afdee3b6ee1a7a7f02
patch
Elsewhere on this site
- python software foundationevery CVE for this vendor
- CWE-407other pages naming this weakness
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.