Vulnerability in Postcss
CVE-2026-9358
A vulnerability was determined in postcss-selector-parser up to 6.1.2/7.1.2. Affected is the function toString of the file src/selectors/container.js of the component AST Serialization. Executing a manipulation can lead to uncontrolled recursion. It is possible to launch the attack remotely. The exploit has been publicly disclosed and may be utilized. Upgrading to version 6.1.3 and 7.1.3 is able to address this issue. This patch is called 5bc698cef66f8abd12610dc623e5d67cbc0f869d. It is suggested to upgrade the affected component. The vendor explains, that according to his definition "DoS on server-side on user-generated CSS is low risk for us (since most users compile own CSS with PostCSS)." The commits were backported to 6.x branch, which was the most downloaded version.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L.
EPSS exploit prediction
EPSS: 0.006 (45.6th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 46th percentile — 45.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.006 · change: +0.003
Affected products
- Postcss — versions 7.1.0, 7.1.1
- Postcss-Selector-Parser — versions 6.1.0, 6.1.1, 6.1.2
Weakness classification (CWE)
References
- vuldb.com/vuln/365321 (technical-description, vdb-entry)
- vuldb.com/vuln/365321/cti (signature, permissions-required)
- vuldb.com/submit/813080 (third-party-advisory)
- gist.github.com/bx33661/581e3a38134601c04e19b4dfc9b459b9 (exploit)
- github.com/postcss/postcss-selector-parser/commit/5bc698cef66f8abd12610dc623e5d… (patch)
- github.com/postcss/postcss-selector-parser/releases/tag/7.1.3 (patch)
- vuldb.com/cve/CVE-2026-9358 (third-party-advisory)
Frequently asked questions
- What is CVE-2026-9358?
- CVE-2026-9358 is a medium-severity vulnerability in Postcss, classified under Improper Resource Shutdown or Release. CVSS score: 4.3/10. Published 2026-05-24.
- How severe is CVE-2026-9358?
- Medium severity. CVSS v3 base score is 4.3 out of 10.