# CVE-2026-126192: Soup Sieve: General sibling combinator inside :has() matches untrusted HTML in quadratic time

Status: published. Published: 2026-11-12. Updated: 2026-11-13.

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.

## Remediation

- fix: soupsieve (PyPI): OSV reports a fixed version 2.10.0. Check the advisory for supported release branches. (source: OSV GHSA-4j63-6c4x-wfg4) — https://github.com/advisories/GHSA-4j63-6c4x-wfg4

## Affected products and versions

- facelessuser / soupsieve: < 2.10 (affected). Source: CNA: GitHub_M
-  / soupsieve (soupsieve): 0.4 (affected, PyPI); 0.5 (affected, PyPI); 0.5.1 (affected, PyPI); 0.5.2 (affected, PyPI); 0.5.3 (affected, PyPI); 0.6 (affected, PyPI); 1.0 (affected, PyPI); 1.0.1 (affected, PyPI); 1.0.2 (affected, PyPI); 1.0b1 (affected, PyPI); 1.0b2 (affected, PyPI); 1.1 (affected, PyPI); 1.2 (affected, PyPI); 1.2.1 (affected, PyPI); 1.3 (affected, PyPI); 1.3.1 (affected, PyPI); 1.4 (affected, PyPI); 1.5 (affected, PyPI); 1.6 (affected, PyPI); 1.6.1 (affected, PyPI); 1.6.2 (affected, PyPI); 1.7 (affected, PyPI); 1.7.1 (affected, PyPI); 1.7.2 (affected, PyPI); 1.7.3 (affected, PyPI); 1.8 (affected, PyPI); 1.9 (affected, PyPI); 1.9.1 (affected, PyPI); 1.9.2 (affected, PyPI); 1.9.3 (affected, PyPI); 1.9.4 (affected, PyPI); 1.9.5 (affected, PyPI); 1.9.6 (affected, PyPI); 2.0 (affected, PyPI); 2.0.1 (affected, PyPI); 2.1 (affected, PyPI); 2.2 (affected, PyPI); 2.2.1 (affected, PyPI); 2.3 (affected, PyPI); 2.3.1 (affected, PyPI); 2.3.2 (affected, PyPI); 2.3.2.post1 (affected, PyPI); 2.4 (affected, PyPI); 2.4.1 (affected, PyPI); 2.5 (affected, PyPI); 2.6 (affected, PyPI); 2.7 (affected, PyPI); 2.8 (affected, PyPI); 2.8.1 (affected, PyPI); 2.8.2 (affected, PyPI); 2.8.3 (affected, PyPI); 2.8.4 (affected, PyPI); 2.9 (affected, PyPI); 2.9.1 (affected, PyPI); 2.9.2 (affected, PyPI); Ecosystem version events: introduced 0; fixed 2.10.0. Source: OSV GHSA-4j63-6c4x-wfg4

## Severity and prioritization

- CVSS 4.0: 6.3 (medium); 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; source: CNA: GitHub_M

- CVSS 4.0: 6.3 (medium); 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; source: NVD: security-advisories@github.com

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: exploitation poc; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-400, CWE-407

## Exploit evidence

- exploit: https://github.com/facelessuser/soupsieve/security/advisories/GHSA-4j63-6c4x-wfg4 (ADP: CISA-ADP)

## References

- https://github.com/facelessuser/soupsieve/security/advisories/GHSA-4j63-6c4x-wfg4 (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/facelessuser/soupsieve/pull/304 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/facelessuser/soupsieve/commit/ffb88cca745c591224f74a8e86414a85e8f35fc0 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/facelessuser/soupsieve/releases/tag/2.10 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/facelessuser/soupsieve/security/advisories/GHSA-4j63-6c4x-wfg4 (ADP: CISA-ADP; exploit)

- https://github.com/facelessuser/soupsieve/commit/ffb88cca745c591224f74a8e86414a85e8f35fc0 (security-advisories@github.com)

- https://github.com/facelessuser/soupsieve/pull/304 (security-advisories@github.com)

- https://github.com/facelessuser/soupsieve/releases/tag/2.10 (security-advisories@github.com)

- https://github.com/facelessuser/soupsieve/security/advisories/GHSA-4j63-6c4x-wfg4 (security-advisories@github.com)

- https://github.com/advisories/GHSA-4j63-6c4x-wfg4 (OSV / GitHub Security Advisories; advisory)

- https://osv.dev/vulnerability/GHSA-4j63-6c4x-wfg4 (OSV / GitHub Security Advisories; osv)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-126192; retrieved 2026-11-13; source updated 2026-11-13

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-126192; retrieved 2026-11-13; source updated 2026-11-12

- OSV / GitHub Security Advisories: https://osv.dev/vulnerability/GHSA-4j63-6c4x-wfg4; retrieved 2026-11-13; source updated 2026-11-13

Revision: fc9c8b7f93cacf74ab5e47603276562afb4005de08e9c8ad3cf240e9d4c47f0f

Canonical: https://y2.dev/cve/CVE-2026-126192

## Agent and API access

Public CVE pages, Markdown, and JSON are free to read without an account or API key.

- Public catalog: https://y2.dev/cve/index.json. Follow nextCursor with the same search, filters, sort, and limit (1–100). A null cursor marks the end.

- WebMCP: search_cve_disclosures, get_cve_disclosure, get_cve_page_markdown, get_y2_cve_access. Available in compatible browsers.

- Cyber API: https://api.y2.dev/api/v2/cyber/cves and https://api.y2.dev/api/v2/cyber/cves/{cveId}.

- Y2 Pro or Elite: create a workspace API key with the intel:cyber scope and send Authorization: Bearer <Y2_API_KEY>. Setup: https://y2.dev/docs/api/create-key.

- x402: Pay per request without an account or API key. Omit Authorization, read the HTTP 402 PAYMENT-REQUIRED challenge, validate its current requirements, and retry with PAYMENT-SIGNATURE through an authorized payment client. These browser tools never make payments. Guide: https://y2.dev/docs/api/x402.

- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

Collected public records only. Check source status for coverage and freshness.