CVSS 6.3 (medium) · published 2026-11-12
Soup Sieve is a CSS selector library designed to be used with Beautiful Soup 4. Prior to 2.10, matching a developer-authored selector that places the general sibling combinator inside :has() repeatedly scans each candidate element's following siblings when the right-hand side is absent, producing quadratic work on attacker-controlled HTML. Applications that evaluate a fixed selector such as div:has(a ~ b) over untrusted markup can have a worker occupied for minutes by a small document, while the adjacent sibling form and trusted-only document processing are not affected in the same way. This issue is fixed in version 2.10.
Weakness: CWE-400, CWE-407
Source: NVD CVE-2026-126192
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