Description
PostCSS Selector Parser is a CSS selector parser that integrates with PostCSS but does not require it. Prior to 7.1.6, src/parser.js splitWord() can receive a flat selector as one word token carrying many class or ID indexes because period and hash characters are not tokenizer word delimiters. The uniqs() deduplication and per-index class and ID membership checks repeatedly scan the class and ID index arrays, while a separate Sass-interpolation filtering pass also performs repeated linear scanning. Together, these passes make parsing quadratic in the number of indexes and allow a crafted selector to occupy a synchronous parser thread. The maxNestingDepth guard does not mitigate the issue because the hostile selector can have zero nesting depth. Only consumers that synchronously parse untrusted selectors in an exposed request path are affected; ordinary build-time parsing of trusted sources is not affected. This issue is fixed in version 7.1.6.
Published: 2026-10-02
Score: 5.9 Medium
EPSS: n/a
KEV: No
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Remediation

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History

Fri, 02 Oct 2026 17:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Fri, 02 Oct 2026 16:00:00 +0000

Type Values Removed Values Added
Description PostCSS Selector Parser is a CSS selector parser that integrates with PostCSS but does not require it. Prior to 7.1.6, src/parser.js splitWord() can receive a flat selector as one word token carrying many class or ID indexes because period and hash characters are not tokenizer word delimiters. The uniqs() deduplication and per-index class and ID membership checks repeatedly scan the class and ID index arrays, while a separate Sass-interpolation filtering pass also performs repeated linear scanning. Together, these passes make parsing quadratic in the number of indexes and allow a crafted selector to occupy a synchronous parser thread. The maxNestingDepth guard does not mitigate the issue because the hostile selector can have zero nesting depth. Only consumers that synchronously parse untrusted selectors in an exposed request path are affected; ordinary build-time parsing of trusted sources is not affected. This issue is fixed in version 7.1.6.
Title PostCSS: Quadratic complexity in flat selector parsing allows CPU exhaustion
Weaknesses CWE-400
CWE-407
References
Metrics cvssV3_1

{'score': 5.9, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H'}

Subscriptions

No data.

cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-10-02T16:16:45.990Z

Reserved: 2026-10-02T14:38:43.243Z

Link: CVE-2026-104844

cve-icon Vulnrichment

Updated: 2026-10-02T16:16:32.699Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-10-02T16:16:46.917

Modified: 2026-10-02T18:44:11.270

Link: CVE-2026-104844

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-02T18:00:04Z

Weaknesses
  • CWE-400

    Uncontrolled Resource Consumption

  • CWE-407

    Inefficient Algorithmic Complexity