GHSA-rj75-hqrm-r3gf: postcss-selector-parser (CVE-2026-104844)

Package	Ecosystem	Affected	Fixed in
postcss-selector-parser	npm	>=7.0.0, <7.1.6 \|\| <6.1.5	7.1.6, 6.1.5

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

Versions of postcss-selector-parser before 6.1.5, and from 7.0.0 before 7.1.6, have a quadratic-complexity flaw in flat selector parsing. A flat selector with many class or id indexes, such as repeated ".a" segments, can take tens of seconds to parse and tie up a thread, so an attacker who can get untrusted selectors parsed synchronously (for example in a sanitizer or online playground) could exhaust CPU. Upgrade to 6.1.5 or 7.1.6; as an interim measure, cap the size of untrusted selectors before parsing.

Written 31 Oct 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

Score	Rating	CVSS	Vector	Source
5.9	Medium	3.1	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H	CNA (GitHub_M)

CISA KEV Not listed.
EPSS 0.0039, the 33rd percentile, on 12 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

31 Oct 2026, 13:33 UTC First seen by agentprime
31 Oct 2026, 13:33 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.