CVE-2026-33170

Rails Active Support has a possible XSS vulnerability in SafeBuffer#%

Severity Score

5.3

*CVSS v4

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

*Multiple Sources

Exploited in Wild

*KEV

Decision

Track

*SSVC

Descriptions

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.

Active Support es un conjunto de herramientas de bibliotecas de soporte y extensiones del núcleo de Ruby extraídas del framework de Rails. Antes de las versiones 8.1.2.1, 8.0.4.1 y 7.2.3.1, 'SafeBuffer#%' no propaga el flag '@html_unsafe' al búfer recién creado. Si un 'SafeBuffer' es mutado in situ (p. ej., a través de 'gsub!') y luego formateado con '%' usando argumentos no confiables, el resultado informa incorrectamente que 'html_safe? == true', omitiendo el auto-escapado de ERB y posiblemente llevando a XSS. Las versiones 8.1.2.1, 8.0.4.1 y 7.2.3.1 contienen un parche.

*Credits: N/A

Attack Vector

Network

Attack Complexity

Low

Attack Requirements

None

Privileges Required

None

User Interaction

Passive

System

Vulnerable | Subsequent

Confidentiality

None

Integrity

Low

None

Availability

None

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Changed

Confidentiality

Low

Integrity

Low

Availability

None

* Common Vulnerability Scoring System

SSVC

Decision:Track

Exploitation

None

Automatable

Tech. Impact

Partial

* Organization's Worst-case Scenario

Timeline

2026-03-17 CVE Reserved
2026-03-23 CVE Published
2026-03-25 CVE Updated
2026-03-29 EPSS Updated
---------- Exploited in Wild
---------- KEV Due Date
---------- First Exploit

CWE

CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

CAPEC

References (7)

URL	Tag	Source
https://github.com/rails/rails/releases/tag/v7.2.3.1	Release Notes
https://github.com/rails/rails/releases/tag/v8.0.4.1	Release Notes
https://github.com/rails/rails/releases/tag/v8.1.2.1	Release Notes

URL	Date	SRC

URL	Date	SRC
https://github.com/rails/rails/commit/50d732af3b7c8aaf63cbcca0becbc00279b215b7	2026-03-24
https://github.com/rails/rails/commit/6e8a81108001d58043de9e54a06fca58962fc2db	2026-03-24
https://github.com/rails/rails/commit/c1ad0e8e1972032f3395853a5e99cea035035beb	2026-03-24

URL	Date	SRC
https://github.com/rails/rails/security/advisories/GHSA-89vf-4333-qx8v	2026-03-24

Affected Vendors, Products, and Versions

Vendor		Product				Version		Other		Status
Vendor	Product	Version	Other	Status	<-- -->	Vendor	Product	Version	Other	Status
Rubyonrails Search vendor "Rubyonrails"		Rails Search vendor "Rubyonrails" for product "Rails"				< 7.2.3.1 Search vendor "Rubyonrails" for product "Rails" and version " < 7.2.3.1"		-		Affected
Rubyonrails Search vendor "Rubyonrails"		Rails Search vendor "Rubyonrails" for product "Rails"				>= 8.0.0 < 8.0.4.1 Search vendor "Rubyonrails" for product "Rails" and version " >= 8.0.0 < 8.0.4.1"		-		Affected
Rubyonrails Search vendor "Rubyonrails"		Rails Search vendor "Rubyonrails" for product "Rails"				>= 8.1.0 < 8.1.2.1 Search vendor "Rubyonrails" for product "Rails" and version " >= 8.1.0 < 8.1.2.1"		-		Affected