Disclosure summary
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.
Source-reported weakness categories
CWE-400, CWE-407
Source-specific records & product guidance
Sources retain their own attribution and scoring. Follow the original record to confirm affected versions, fixed releases, and configuration conditions.
GitHub Reviewed Security Advisories · GHSA-rj75-hqrm-r3gf
Open original source · Updated Oct 05, 2026
PostCSS: Quadratic complexity in flat selector parsing allows CPU exhaustion
Source severity: MEDIUM / 0
| Ecosystem | Package | Affected range | First patched |
|---|---|---|---|
| npm | postcss-selector-parser | < 7.1.6 | 7.1.6 |
NIST National Vulnerability Database · NVD-CVE-2026-104844
Open original source · Updated Oct 02, 2026
Only CPE matches marked vulnerable=true are indexed. AND/OR platform conditions must be checked in the original NVD record.
Original records & references
PUBLISHED 2026-10-02T12:16:46-04:00
MODIFIED 2026-10-02T14:44:11-04:00
INGESTED 2026-10-06T11:45:30-04:00