Sanitize vulnerable to Cross-site Scripting via insufficient neutralization of style element content

Exploitation

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

CVSS

7.1 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L

EPSS

• CVE-2023-36823: 0.71% estimated exploitation activity in the next 30 days; percentile 53.63 (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.

Impact Using carefully crafted input, an attacker may be able to sneak arbitrary HTML and CSS through Sanitize = 3.0.0, < 6.0.2 when Sanitize is configured to use the built-in "relaxed" config or when using a custom config that allows style elements and one or more CSS at-rules. This could result in XSS (cross-site scripting) or other undesired behavior when the malicious HTML and CSS are rendered in a browser. Patches Sanitize = 6.0.2 performs additional escaping of CSS in style element content, which fixes this issue. Workarounds Users who are unable to upgrade can prevent this issue by using a Sanitize config that doesn't allow style elements, using a Sanitize config that doesn't allow CSS at-rules, or by manually escaping the character sequence </ as <\/ in style element content. Credit This issue was found by @cure53 during an audit of a project that uses Sanitize and was reported by one of that project's maintainers. Thank you!

Published by the source

6 Jul 2023, 19:45 UTC

Last modified by the source

23 Nov 2023, 05:05 UTC

Source last checked

26 Oct 2026, 15:48 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-f5ww-cq3m-q3g7

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# Patch Next advisory brief: CVE-2023-36823

Advisory: Sanitize vulnerable to Cross-site Scripting via insufficient neutralization of `style` element content
IDs: CVE-2023-36823, GHSA-f5ww-cq3m-q3g7
Record: https://patchnext.com/advisories/cve-2023-36823 (revision 1, source checked 26 Oct 2026, 15:48 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: sanitize 6.0.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems sanitize: affected >= 3.0.0, < 6.0.2; fixed in 6.0.2

## Suggested inspection (read-only)
- RubyGems sanitize: check the installed version with your package manager.

## 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 sanitize.
- 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://github.com/advisories/GHSA-f5ww-cq3m-q3g7 (GitHub-reviewed advisory GHSA-f5ww-cq3m-q3g7 lists affected ranges: RubyGems sanitize >=3.0.0 <6.0.2)

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