CVE-2024-28121: stimulus_reflex is a system to extend the capabilities of both Rails and Stimulus by intercepting user interactions and passing them to Rails over rea...

Description

stimulus_reflex is a system to extend the capabilities of both Rails and Stimulus by intercepting user interactions and passing them to Rails over real-time websockets. In affected versions more methods than expected can be called on reflex instances. Being able to call some of them has security implications. To invoke a reflex a websocket message of the following shape is sent: `\"target\":\"[class_name]#[method_name]\",\"args\":[]`. The server will proceed to instantiate `reflex` using the provided `class_name` as long as it extends `StimulusReflex::Reflex`. It then attempts to call `method_name` on the instance with the provided arguments. This is problematic as `reflex.method method_name` can be more methods that those explicitly specified by the developer in their reflex class. A good example is the instance_variable_set method. This vulnerability has been patched in versions 3.4.2 and 3.5.0.rc4. Users unable to upgrade should: see the backing GHSA advisory for mitigation advice.

Metrics

CVSS 3.1

8.8/10

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

1.55%

72.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-470

Affected Software

Vendor	Product	Versions	Update
Stimulusreflex	Stimulusrelfex	< 3.4.2	—
Stimulusreflex	Stimulusrelfex	3.5.0	Pre1

References

http://seclists.org/fulldisclosure/2024/Mar/16Exploit, Third Party Advisory
https://github.com/stimulusreflex/stimulus_reflex/blob/0211cad7d60fe96838587f159d657e44cee51b9b/app/channels/stimulus_reflex/channel.rb#L83Technical Description
https://github.com/stimulusreflex/stimulus_reflex/commit/538582d240439aab76066c72335ea92096cd0c7fPatch
https://github.com/stimulusreflex/stimulus_reflex/releases/tag/v3.4.2Product, Release Notes
https://github.com/stimulusreflex/stimulus_reflex/releases/tag/v3.5.0.rc4Product, Release Notes
https://github.com/stimulusreflex/stimulus_reflex/security/advisories/GHSA-f78j-4w3g-4q65Exploit, Vendor Advisory
http://seclists.org/fulldisclosure/2024/Mar/16Exploit, Third Party Advisory
https://github.com/stimulusreflex/stimulus_reflex/blob/0211cad7d60fe96838587f159d657e44cee51b9b/app/channels/stimulus_reflex/channel.rb#L83Technical Description
https://github.com/stimulusreflex/stimulus_reflex/commit/538582d240439aab76066c72335ea92096cd0c7fPatch
https://github.com/stimulusreflex/stimulus_reflex/releases/tag/v3.4.2Product, Release Notes
https://github.com/stimulusreflex/stimulus_reflex/releases/tag/v3.5.0.rc4Product, Release Notes
https://github.com/stimulusreflex/stimulus_reflex/security/advisories/GHSA-f78j-4w3g-4q65Exploit, Vendor Advisory

Timeline

Published: Mar 12, 2024
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2024-28121?

stimulus_reflex is a system to extend the capabilities of both Rails and Stimulus by intercepting user interactions and passing them to Rails over real-time websockets. In affected versions more methods than expected can be called on reflex instances. Being able to call some of them has security implications. To invoke a reflex a websocket message of the following shape is sent: `\"target\":\"[class_name]#[method_name]\",\"args\":[]`. The server will proceed to instantiate `reflex` using the provided `class_name` as long as it extends `StimulusReflex::Reflex`. It then attempts to call `method_name` on the instance with the provided arguments. This is problematic as `reflex.method method_name` can be more methods that those explicitly specified by the developer in their reflex class. A good example is the instance_variable_set method. This vulnerability has been patched in versions 3.4.2 and 3.5.0.rc4. Users unable to upgrade should: see the backing GHSA advisory for mitigation advice.

How severe is CVE-2024-28121?

CVE-2024-28121 has a CVSS score of 8.8/10 (HIGH severity). The EPSS model estimates a 1.55% probability of exploitation in the next 30 days.

How do I fix CVE-2024-28121?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.