Service interruption via quadratic XPath predicate evaluation
Published Jul 28, 2026 · Updated Jul 28, 2026
Algorithmic complexity in CPython before 3.14.7 and 3.15.0a1 through 3.15.0rc1 allows attackers to interrupt services via crafted XML. ElementPath's index-predicate selector repeatedly searches the parent's same-tag children for every candidate instead of reusing the indexed sibling, producing quadratic work. Reachability requires an application to evaluate attacker-shaped XML with positional predicates through findall(), a consumed iterfind(), or a late-matching find(); the bounded consequence is excessive CPU use.
Summary
What happened
Algorithmic complexity in CPython before 3.14.7 and 3.15.0a1 through 3.15.0rc1 allows attackers to interrupt services via crafted XML. ElementPath's index-predicate selector repeatedly searches the parent's same-tag children for every candidate instead of reusing the indexed sibling, producing quadratic work. Reachability requires an application to evaluate attacker-shaped XML with positional predicates through findall(), a consumed iterfind(), or a late-matching find(); the bounded consequence is excessive CPU use.
The record
- CVE
- CVE-2026-6879
- Published
- Jul 28, 2026
- Updated
- Jul 28, 2026
- Vendor
- Python Software Foundation
- Product
- CPython
- Classifications
- CWE-407, T1499.004
- Attack vector
- Unavailable
- Privileges
- Unavailable
Timeline
How it unfolded
- Jul 28, 2026CVE publishedPublication date reported by the CVE source.
- Jul 28, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
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- Affected versionversion=0 <3.15.0
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
What attackers are doing with it
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Weakness, pattern, technique
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Technologies
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Your stack
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