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.
Scores
CVSS v3
6.1
EPSS
0.0001
EPSS Percentile
2.8%
Attack Vector
NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
CISA SSVC
Vulnrichment
Exploitation
none
Automatable
no
Technical Impact
partial
Details
CWE
CWE-79
Status
published
Products (5)
rails/activesupport
< 7.2.3.1
rails/activesupport
>= 8.0.0.beta1, < 8.0.4.1
rails/activesupport
>= 8.1.0.beta1, < 8.1.2.1
rubygems/activesupport
8.1.0.beta1 - 8.1.2.1RubyGems
rubyonrails/rails
< 7.2.3.1
Published
Mar 24, 2026
Tracked Since
Mar 24, 2026