TI-2026-66130 Aliases CVE-2026-104844 GHSA-rj75-hqrm-r3gf

PostCSS: Quadratic complexity in flat selector parsing allows CPU exhaustion

LOW 27CWE-400Published 2026-10-02 · Updated 2026-10-02

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: High
Impact type: Denial of service
Confidentiality · integrity · availability: None · None · High
Fix status: Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-400.

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00389 33rd percentileScored 2026-11-07

Fix Fixed postcss-selector-parser (postcss): 7.1.6postcss-selector-parser (npm): 7.1.6, 6.1.5

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: No
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
postcss	postcss-selector-parser	before 7.1.6	7.1.6	Patch available	CNA
—	postcss-selector-parser (npm)	7.0.0 to before 7.1.6	7.1.6	Patch available	GHSA-rj75-hqrm-r3gf
—	postcss-selector-parser (npm)	before 6.1.5	6.1.5	Patch available	GHSA-rj75-hqrm-r3gf

postcss-selector-parser Vendorpostcss Affected before 7.1.6 Fixed in 7.1.6 Patch available CNA
postcss-selector-parser (npm) Vendor— Affected 7.0.0 to before 7.1.6 Fixed in 7.1.6 Patch available GHSA-rj75-hqrm-r3gf
postcss-selector-parser (npm) Vendor— Affected before 6.1.5 Fixed in 6.1.5 Patch available GHSA-rj75-hqrm-r3gf

Remediation

Fix · CNA postcss-selector-parser (postcss) Fixed in 7.1.6
Fix · GHSA-rj75-hqrm-r3gf postcss-selector-parser (npm) Fixed in 7.1.6 Advisory →
Fix · GHSA-rj75-hqrm-r3gf postcss-selector-parser (npm) Fixed in 6.1.5 Advisory →

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

Not affected: 1 product

Red Hat Hardened Images

Timeline

2026-10-02 Threatist record created from CVE-2026-104844
2026-10-06 Alias added: GHSA-rj75-hqrm-r3gf
2026-10-06 Fix available: npm/[email protected] · GHSA-rj75-hqrm-r3gf
2026-10-06 CVSS score added · GHSA-rj75-hqrm-r3gf
2026-10-06 Weakness changed · GHSA-rj75-hqrm-r3gf
2026-10-06 5 new references · GHSA-rj75-hqrm-r3gf

References

Advisory 1

https://nvd.nist.gov/vuln/detail/CVE-2026-104844

Other 7

TI-2026-33367 PostCSS: Arbitrary file read and information disclosure via attacker-controlled sourceMappingURL in CSS comments CVSS 3.1CRITICAL 9.1
TI-2026-51730 PostCSS: Path Traversal in Previous Source Map Auto-Loading (sourceMappingURL) leads to Arbitrary .map File Disclosure CVSS 3.1HIGH 7.5
TI-2026-48533 Information disclosure in postcss CVSS 4.0MEDIUM 6.3
TI-2026-29908 PostCSS has XSS via Unescaped </style> in its CSS Stringify Output CVSS 3.1MEDIUM 6.1
TI-2021-06075 Regular expression denial of service (ReDoS) in postcss CVSS 3.1HIGH 7.5
TI-2023-23794 An issue was discovered in PostCSS before 8.4.31. CVSS 3.1MEDIUM 5.3

See all 7 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences