CVE-2026-104844

MEDIUMCVSS 5.9/10

Last modified

CVE-2026-104844 is a medium-severity vulnerability rated 5.9/10 on the CVSS scale. 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.

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.

Metrics

Weakness Enumeration

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
postcsspostcss-selector-parser< 7.1.6

References

Timeline

Published
Last Modified
Status
Awaiting Analysis

Frequently Asked Questions

What is CVE-2026-104844?
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.
How severe is CVE-2026-104844?
CVE-2026-104844 has a CVSS score of 5.9/10 (MEDIUM severity).
How do I fix CVE-2026-104844?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST