PostCSS line return parsing error

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

EPSS

• CVE-2023-44270: 0.97% estimated exploitation activity in the next 30 days; percentile 62.07 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

An issue was discovered in PostCSS before 8.4.31. It affects linters using PostCSS to parse external Cascading Style Sheets (CSS). There may be \r discrepancies, as demonstrated by @font-face{ font:(\r/);} in a rule. This vulnerability affects linters using PostCSS to parse external untrusted CSS. An attacker can prepare CSS in such a way that it will contains parts parsed by PostCSS as a CSS comment. After processing by PostCSS, it will be included in the PostCSS output in CSS nodes (rules, properties) despite being originally included in a comment.

Published by the source

30 Sep 2023, 00:31 UTC

Last modified by the source

10 Sep 2026, 03:49 UTC

Source last checked

26 Oct 2026, 12:38 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-7fh5-64p2-3v2j

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-7fh5-64p2-3v2j

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# Patch Next advisory brief: CVE-2023-44270

Advisory: PostCSS line return parsing error
IDs: CVE-2023-44270, GHSA-7fh5-64p2-3v2j
Record: https://patchnext.com/advisories/cve-2023-44270 (revision 2, source checked 26 Oct 2026, 12:38 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: postcss 8.4.31. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm postcss: affected < 8.4.31; fixed in 8.4.31

## Suggested inspection (read-only)
- `npm ls postcss --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on postcss.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-7fh5-64p2-3v2j (OSV record GHSA-7fh5-64p2-3v2j lists affected ranges: npm postcss >=0 <8.4.31 (fixed))
- Verified: https://github.com/advisories/GHSA-7fh5-64p2-3v2j (GitHub-reviewed advisory GHSA-7fh5-64p2-3v2j lists affected ranges: npm postcss >=0 <8.4.31)

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