# PostCSS: Quadratic complexity in flat selector parsing allows CPU exhaustion Advisory record · `GHSA-rj75-hqrm-r3gf` - **Identifiers:** `GHSA-rj75-hqrm-r3gf` · `CVE-2026-104844` - **State:** Confirmed - **Severity:** CVSS 5.9 Medium - **Critical:** No - **Weakness (CWE):** [CWE-400](https://cwe.mitre.org/data/definitions/400.html) · [CWE-407](https://cwe.mitre.org/data/definitions/407.html) - **Tags:** [Denial of service](https://agentprime.io/advisories/tag/dos.md) - **Published:** 5 Oct 2026 - **Updated:** 26 Oct 2026 - **Reviewed by a person:** No Published by the GitHub Advisory Database at 5 Oct 2026, 22:53 UTC. agentprime has not analysed this yet, so whether it affects any app is not known. ## Affected packages - `postcss-selector-parser` (npm): affected `>=7.0.0, <7.1.6 || <6.1.5`; fixed in `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 - 5.9 Medium, CVSS 3.1: `CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H`, from 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](https://osv.dev/vulnerability/GHSA-rj75-hqrm-r3gf) ## Sources - [GitHub Advisory Database: GHSA-rj75-hqrm-r3gf](https://github.com/advisories/GHSA-rj75-hqrm-r3gf) - [OSV: GHSA-rj75-hqrm-r3gf](https://osv.dev/vulnerability/GHSA-rj75-hqrm-r3gf) - - - - - - - - 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. ## Check whether this affects you A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet. - With the agentprime MCP server (), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: - In a browser: reads your lockfile in the browser, never uploading it. - Whether it touches your code, with file and line: the Claude Code plugin, - As JSON: , or `POST https://api.agentprime.io/v1/match` with your packages () --- The web page: . Everything for agents: .