CVE-2026-45623: PostCSS takes a CSS file and provides an API to analyze and modify its rules by transforming the rules into an

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HIGH 7.5REMOTEUPGRADE

CVE-2026-45623 is a high-severity flaw (CVSS 7.5) affecting postcss. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 re

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.6% (top 51%)
CISA exploited list	No
Weakness	CWE-22, CWE-200
Published	2026-07-27
Last modified	2026-08-07

Publisher (CNA): GitHub, Inc. · Vendor: postcss

Last updated 2026-08-07 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-27 18:16 UTCPublished CVE record published
2026-08-07 00:13 UTCUpdated Record last modified

postcss postcss UPGRADE

Affected: < 8.5.12

Fixed in: 8.5.12

Safe to downgrade to: no unaffected older release

1. Check installed version

npm ls postcss

2. UPGRADE to 8.5.12

npm install postcss@">=8.5.12"

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-45623?

postcss: upgrade to 8.5.12. Exact commands for each OS are on this page.

Is CVE-2026-45623 being exploited?

CVE-2026-45623 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-45623 affect?

CVE-2026-45623 affects postcss. Severity is high (CVSS 7.5). 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

How urgent is CVE-2026-45623?

Priority 48/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-69153 MEDIUM 5.3 UPGRADE PostCSS takes a CSS file and provides an API to analyze and modify its rules by transforming the rules into an

References

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