Description
Active Support is a toolkit of support libraries and Ruby core extensions extracted from the Rails framework. Prior to versions 8.1.2.1, 8.0.4.1, and 7.2.3.1, `SafeBuffer#%` does not propagate the `@html_unsafe` flag to the newly created buffer. If a `SafeBuffer` is mutated in place (e.g. via `gsub!`) and then formatted with `%` using untrusted arguments, the result incorrectly reports `html_safe? == true`, bypassing ERB auto-escaping and possibly leading to XSS. Versions 8.1.2.1, 8.0.4.1, and 7.2.3.1 contain a patch.
Published: 2026-03-23
Score: 5.3 Medium
EPSS: < 1% Very Low
KEV: No
Impact: Cross‑Site Scripting
Action: Immediate Patch
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Remediation

No vendor fix or workaround currently provided.

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Tracking

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-89vf-4333-qx8v Rails Active Support has a possible XSS vulnerability in SafeBuffer#%
History

Wed, 25 Mar 2026 20:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Tue, 24 Mar 2026 18:00:00 +0000

Type Values Removed Values Added
First Time appeared Rubyonrails
Rubyonrails rails
CPEs cpe:2.3:a:rubyonrails:rails:*:*:*:*:*:*:*:*
Vendors & Products Rubyonrails
Rubyonrails rails
Metrics cvssV3_1

{'score': 5.4, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N'}

cvssV3_1

{'score': 6.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N'}


Tue, 24 Mar 2026 12:15:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

cvssV3_1

{'score': 5.4, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N'}

threat_severity

Moderate


Tue, 24 Mar 2026 10:45:00 +0000

Type Values Removed Values Added
First Time appeared Rails
Rails activesupport
Vendors & Products Rails
Rails activesupport

Tue, 24 Mar 2026 02:30:00 +0000

Type Values Removed Values Added
Description Active Support is a toolkit of support libraries and Ruby core extensions extracted from the Rails framework. Prior to versions 8.1.2.1, 8.0.4.1, and 7.2.3.1, `SafeBuffer#%` does not propagate the `@html_unsafe` flag to the newly created buffer. If a `SafeBuffer` is mutated in place (e.g. via `gsub!`) and then formatted with `%` using untrusted arguments, the result incorrectly reports `html_safe? == true`, bypassing ERB auto-escaping and possibly leading to XSS. Versions 8.1.2.1, 8.0.4.1, and 7.2.3.1 contain a patch.
Title Rails Active Support has a possible XSS vulnerability in SafeBuffer#%
Weaknesses CWE-79
References
Metrics cvssV4_0

{'score': 5.3, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N'}


Subscriptions

Rails Activesupport
Rubyonrails Rails
cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-03-25T19:20:28.280Z

Reserved: 2026-03-17T21:17:08.888Z

Link: CVE-2026-33170

cve-icon Vulnrichment

Updated: 2026-03-25T19:20:23.878Z

cve-icon NVD

Status : Analyzed

Published: 2026-03-24T00:16:28.287

Modified: 2026-03-24T18:00:00.080

Link: CVE-2026-33170

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-03-23T23:09:48Z

Links: CVE-2026-33170 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-03-25T20:36:06Z

Weaknesses