VYPR
← All advisories
Moderate severityNVD Advisory· Published Sep 29, 2023· Updated Nov 3, 2025

CVE-2023-44270

CVE-2023-44270

Description

PostCSS before 8.4.31 mishandles CSS comments, enabling attackers to bypass linters by injecting nodes inside comment syntax.

AI Insight

LLM-synthesized narrative grounded in this CVE's description and references.

PostCSS before 8.4.31 mishandles CSS comments, enabling attackers to bypass linters by injecting nodes inside comment syntax.

Vulnerability

Description PostCSS versions prior to 8.4.31 contain a parsing flaw where CSS content placed inside comments is incorrectly interpreted as actual CSS nodes (rules, properties) after processing [2]. This occurs because the tokenizer does not properly distinguish comment boundaries, leading to comment content being treated as legitimate CSS structures.

Exploitation

An attacker can craft a malicious CSS input that appears to contain comments but actually includes hidden rules or properties. When a linter or other tool using PostCSS parses this input, the hidden content is preserved in the output, potentially bypassing security checks or style validations [2]. No authentication is required; the attack vector is delivering untrusted CSS to a vulnerable PostCSS instance.

Impact

Successful exploitation allows an attacker to inject arbitrary CSS rules that may override intended styles, exfiltrate data via CSS-based attacks, or bypass linter rules that rely on the assumption that comments are ignored. This is particularly concerning for applications that accept external CSS and use PostCSS for linting or transformation.

Mitigation

The vulnerability is fixed in PostCSS version 8.4.31 [3]. Users should update immediately. No workarounds are available for earlier versions.

References
  1. NVD - CVE-2023-44270
  2. Release 8.4.31 · postcss/postcss

AI Insight generated on May 20, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.

Affected packages

Versions sourced from the GitHub Security Advisory.

PackageAffected versionsPatched versions
postcssnpm
< 8.4.318.4.31

Affected products

3

Patches

1
58cc860b4c17

Fix carrier return parsing

https://github.com/postcss/postcssAndrey SitnikSep 28, 2023via ghsa
commit
2 files changed · +7 −1
  • lib/tokenize.js+1 −1 modified
    @@ -22,7 +22,7 @@ const AT = '@'.charCodeAt(0)
 
 const RE_AT_END = /[\t\n\f\r "#'()/;[\\\]{}]/g
 const RE_WORD_END = /[\t\n\f\r !"#'():;@[\\\]{}]|\/(?=\*)/g
-const RE_BAD_BRACKET = /.[\n"'(/\\]/
+const RE_BAD_BRACKET = /.[\r\n"'(/\\]/
 const RE_HEX_ESCAPE = /[\da-f]/i
 
 module.exports = function tokenizer(input, options = {}) {
  • test/parse.test.ts+6 −0 modified
    @@ -34,6 +34,12 @@ test('should has false at hasBOM property', () => {
   is(css.first?.source?.input.hasBOM, false)
 })
 
+test('parses carrier return', () => {
+  throws(() => {
+    parse('@font-face{ font:(\r/*);} body { a: "a*/)} a{}"}')
+  }, /:1:46: Unclosed string/)
+})
+
 test('saves source file', () => {
   let css = parse('a {}', { from: 'a.css' })
   is(css.first?.source?.input.css, 'a {}')

Vulnerability mechanics

Generated on May 9, 2026. Inputs: CWE entries + fix-commit diffs from this CVE's patches. Citations validated against bundle.

References

7

News mentions

0

No linked articles in our index yet.