Soup Sieve: General sibling combinator inside :has() matches untrusted HTML in quadratic time

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-126192
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-11-12 17:17:32 UTC
Updated2026-11-12 19:09:06 UTC
DescriptionSoup 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.

Risk And Classification

Primary CVSS: v4.0 6.3 MEDIUM from [email protected]

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Problem Types: CWE-400 | CWE-407 | CWE-400 CWE-400: Uncontrolled Resource Consumption | CWE-407 CWE-407: Inefficient Algorithmic Complexity

VersionSourceTypeScoreSeverityVector
4.0[email protected]Secondary6.3MEDIUMCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/C...
4.0CNADECLARED6.3MEDIUMCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

CVSS v4.0 Breakdown

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
Present
Privileges Required
None
User Interaction
None
Confidentiality
None
Integrity
None
Availability
Low
Sub Conf.
None
Sub Integrity
None
Sub Availability
None

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Facelessuser Soupsieve affected < 2.10 Not specified

References

ReferenceSourceLinkTags
github.com/facelessuser/soupsieve/security/advisories/GHSA-4j63-6c4x-wfg4 [email protected] github.com
github.com/facelessuser/soupsieve/pull/304 [email protected] github.com
github.com/facelessuser/soupsieve/commit/ffb88cca745c591224f74a8e86414a8... [email protected] github.com
github.com/facelessuser/soupsieve/releases/tag/2.10 [email protected] github.com
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