CVE-2026-33170
March 23, 2026
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.
Affected Packages
https://github.com/rails/rails.git (GITHUB):
Affected version(s) >=v8.1.0 <v8.1.3Fix Suggestion:
Update to version v8.1.3https://github.com/rails/rails.git (GITHUB):
Affected version(s) =v8.1.2 <v8.1.2.1Fix Suggestion:
Update to version v8.1.2.1https://github.com/rails/rails.git (GITHUB):
Affected version(s) >=v8.0.0 <v8.0.4.1Fix Suggestion:
Update to version v8.0.4.1https://github.com/rails/rails.git (GITHUB):
Affected version(s) =v7.2.3 <v7.2.3.1Fix Suggestion:
Update to version v7.2.3.1https://github.com/rails/rails.git (GITHUB):
Affected version(s) >=v8.0.0 <v8.0.5Fix Suggestion:
Update to version v8.0.5activesupport (RUBY):
Affected version(s) >=8.1.0.beta1 <8.1.2.1Fix Suggestion:
Update to version 8.1.2.1activesupport (RUBY):
Affected version(s) >=1.0.0 <7.2.3.1Fix Suggestion:
Update to version 7.2.3.1activesupport (RUBY):
Affected version(s) >=8.0.0.beta1 <8.0.4.1Fix Suggestion:
Update to version 8.0.4.1Related Resources (9)
Do you need more information?
Contact UsCVSS v4
Base Score:
5.3
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
NONE
User Interaction
PASSIVE
Vulnerable System Confidentiality
NONE
Vulnerable System Integrity
LOW
Vulnerable System Availability
NONE
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
4.3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
NONE
Integrity
LOW
Availability
NONE
Weakness Type (CWE)
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
EPSS
Base Score:
0.02
