Possible XSS Security Vulnerability in SafeBuffer#bytesplice

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-2023-28120: 0.95% estimated exploitation activity in the next 30 days; percentile 61.22 (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.

There is a vulnerability in ActiveSupport if the new bytesplice method is called on a SafeBuffer with untrusted user input. This vulnerability has been assigned the CVE identifier CVE-2023-28120. Versions Affected: All. Not affected: None Fixed Versions: 7.0.4.3, 6.1.7.3 Impact ActiveSupport uses the SafeBuffer string subclass to tag strings as htmlsafe after they have been sanitized. When these strings are mutated, the tag is should be removed to mark them as no longer being htmlsafe. Ruby 3.2 introduced a new bytesplice method which ActiveSupport did not yet understand to be a mutation. Users on older versions of Ruby are likely unaffected. All users running an affected release and using bytesplice should either upgrade or use one of the workarounds immediately. Workarounds Avoid calling bytesplice on a SafeBuffer (htmlsafe) string with untrusted user input.

Published by the source

15 Mar 2023, 21:36 UTC

Last modified by the source

10 Jan 2025, 13:51 UTC

Source last checked

26 Oct 2026, 15:48 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-pj73-v5mw-pm9j

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# Patch Next advisory brief: CVE-2023-28120

Advisory: Possible XSS Security Vulnerability in SafeBuffer#bytesplice
IDs: CVE-2023-28120, GHSA-pj73-v5mw-pm9j
Record: https://patchnext.com/advisories/cve-2023-28120 (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: 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: activesupport 7.0.4.3, 6.1.7.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems activesupport: affected >= 7.0.0, < 7.0.4.3; < 6.1.7.3; fixed in 6.1.7.3, 7.0.4.3

## Suggested inspection (read-only)
- RubyGems activesupport: 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 activesupport.
- 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-pj73-v5mw-pm9j (GitHub-reviewed advisory GHSA-pj73-v5mw-pm9j lists affected ranges: RubyGems activesupport >=7.0.0 =0 <6.1.7.3)

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