CVE-2026-41305
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedPostCSS takes a CSS file and provides an API to analyze and modify its rules by transforming the rules into an Abstract Syntax Tree. Versions prior to 8.5.10 do not escape `</style>` sequences when stringifying CSS ASTs. When user-submitted CSS is parsed and re-stringified for embedding in HTML `<style>` tags, `</style>` in CSS values breaks out of the style context, enabling XSS. Version 8.5.10 fixes the issue.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidencePostCSS versions before 8.5.10 fail to escape `</style>` sequences when stringifying CSS ASTs. When user-submitted CSS is parsed and re-stringified for embedding in HTML `<style>` tags, the unescaped `</style>` in CSS values breaks out of the style context, allowing XSS attacks.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- Required
- Scope
- Changed
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify installed PostCSS versionRun 'npm list postcss' or check package.json dependencies to see the installed version of the postcss packageAffected if The installed version is earlier than 8.5.10 (e.g., 8.5.9, 8.4.x, 8.3.x, etc.)
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Locate PostCSS in dependenciesSearch for 'postcss' in package.json, package-lock.json, or yarn.lock files within the projectAffected if PostCSS is listed as a dependency at a version below 8.5.10
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Identify CSS processing code pathsSearch the codebase for usages of PostCSS API methods such as postcss.parse() followed by .toString() or .root().toString() that process CSS inputAffected if Code parses CSS and stringifies it for output, especially if the CSS source is user-provided
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Check for HTML style embeddingSearch for code that takes stringified CSS and embeds it directly into HTML <style> tags (e.g., string concatenation with '<style>' + css + '</style>')Affected if Stringified CSS output is embedded directly into HTML style tags without additional escaping of '</style>' sequences
A user is affected if PostCSS version is below 8.5.10 AND their application parses user-submitted CSS and embeds the stringified output into HTML <style> tags.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scopedUpgrade PostCSS to version 8.5.10 or later. Additionally, audit any code paths that parse user-submitted CSS and embed it in HTML style tags to ensure proper escaping.
PostCSS version 8.5.10
- Check the current version of PostCSS installed in your project by running: npm list postcss or yarn list postcss
- Upgrade PostCSS to version 8.5.10 or later by running: npm update postcss@^8.5.10 or yarn add postcss@^8.5.10
- Verify the upgrade was successful by checking the installed version: npm list postcss
- If you use PostCSS as a transitive dependency, ensure all direct dependencies that depend on PostCSS are compatible with version 8.5.10 by running npm update
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation2.0 h
- Testing3.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-41305 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-41305 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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