Skip to main content
HIGH

CVE-2026-45623

CVSS v3

7.5

HIGH

EPSS Score

0.6 %

exploit probability, as of 2026-10-17

CISA KEV

No

known exploited

Exploitation

—

SSVC status

Get an alert for each new CVE published for postcss. Watch postcss in CVE Watch Free account · no credit card

Affected and fixed versions

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • postcssnpmall versions · fixed in 8.5.12

Vendor advisories

  • CVE-2026-45623 Red Hat Product Security194 products fixed · 40 known affected

    postcss: PostCSS: Information disclosure and denial of service via crafted CSS input

    cryostat-openshift-console-plugin-npm as a component of Cryostat 4 · grafana-infinity-datasource-npm as a component of Cryostat 4 · postcss as a component of Cryostat 4

  • RHSA-2026:83598 Red Hat Product Security1 product fixed

    Red Hat Security Advisory: RHTAS 1.4.4 - Red Hat Trusted Artifact Signer Release

  • RHSA-2026:74621 Red Hat Product Security1 product fixed

    Red Hat Security Advisory: General availability of the satellite/iop-advisor-frontend-rhel9 container image

  • RHSA-2026:74609 Red Hat Product Security4 products fixed

    Red Hat Security Advisory: Cluster Observability Operator 1.5.3

  • RHSA-2026:74503 Red Hat Product Security15 products fixed

    Red Hat Security Advisory: Satellite 6.19.5 Async Update

  • RHSA-2026:70587 Red Hat Product Security4 products fixed

    Red Hat Security Advisory: OpenShift Container Platform 4.17.58 bug fix and security update

34 more advisories

Full record on NVD

Description

PostCSS takes a CSS file and provides an API to analyze and modify its rules by transforming the rules into an Abstract Syntax Tree. In versions 8.5.11 and prior, the PreviousMap parses the /*# sourceMappingURL=PATH */ comment from any CSS string passed to process() and dereferences PATH against the local filesystem with no scheme, allowlist, or traversal check. An attacker who controls the CSS input can cause the host process to read any file readable by Node and leak the first ~10 bytes of its content through the resulting JSON.parse SyntaxError message. The bug also yields a precise file-existence oracle and a controllable-read primitive that may be combined with large-file targets for DoS. The behaviour is triggered with PostCSS's default options — no from, no map, no plugins required — and is therefore reachable from any pipeline that runs untrusted CSS through PostCSS (CMS themes, user-uploaded styles, browser-extension/userstyle processors, build pipelines for third-party packages, blog comment renderers, etc.). This issue has been fixed in version 8.5.12.

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Published
2026-07-27
Last Modified
2026-07-27

Frequently asked questions

What is CVE-2026-45623?

PostCSS takes a CSS file and provides an API to analyze and modify its rules by transforming the rules into an Abstract Syntax Tree. In versions 8.5.11 and prior, the PreviousMap parses the /*# sourceMappingURL=PATH */ comment from any CSS string passed to process() and dereferences PATH against the local filesystem with no scheme, allowlist, or traversal check. An attacker who controls the CSS input can cause the host process to read any file readable by Node and leak the first ~10 bytes of its content through the resulting JSON.parse SyntaxError message. The bug also yields a precise file-existence oracle and a controllable-read primitive that may be combined with large-file targets for DoS. The behaviour is triggered with PostCSS's default options — no from, no map, no plugins required — and is therefore reachable from any pipeline that runs untrusted CSS through PostCSS (CMS themes, user-uploaded styles, browser-extension/userstyle processors, build pipelines for third-party packages, blog comment renderers, etc.). This issue has been fixed in version 8.5.12.

Is CVE-2026-45623 actively exploited?

Active exploitation of CVE-2026-45623 has not been confirmed. Its EPSS score was 0.6% on 2026-10-17, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-45623?

CVE-2026-45623 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.

Running postcss? Hear about its next vulnerability

CVE Watch matches each new CVE to the vendors and products you list (vendor and product, not the version) and puts it in your alerts with its KEV and EPSS status.

Get alerts for this productCISA KEV additions, October 2026Search CVEs

Already have an account? Open CVE WatchNo credit card required · 50 free checks/month · Free API key

Go further

Related vulnerabilities

Same product first, then the same vendor advisory and the same publication week.

Back to CVE Database