CVE-2026-33167
Cross-Site Scripting in Action Pack Debug Exceptions Page
Publication date: 2026-03-23
Last updated on: 2026-03-23
Assigner: GitHub, Inc.
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| rubygems | action_pack | to 8.1.2.1 (exc) |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-79 | The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
This vulnerability exists in the Action Pack Rubygem, which is used for building web applications on the Rails framework. In versions before 8.1.2.1 on the 8.1 branch, the debug exceptions page does not properly escape exception messages.
Because of this improper escaping, a specially crafted exception message can inject arbitrary HTML and JavaScript into the debug exceptions page, resulting in a cross-site scripting (XSS) vulnerability.
This issue affects applications that have detailed exception pages enabled (with the setting `config.consider_all_requests_local = true`), which is the default setting in development environments.
The vulnerability was fixed in version 8.1.2.1 of Action Pack.
How can this vulnerability impact me? :
This vulnerability can allow an attacker to execute arbitrary HTML and JavaScript code in the context of the debug exceptions page.
If an attacker can trigger an exception with a crafted message, they could exploit this to perform cross-site scripting (XSS) attacks.
Such XSS attacks could lead to theft of sensitive information, session hijacking, or other malicious actions within the affected application's development environment.
However, since this vulnerability affects the debug exceptions page which is typically enabled only in development, the risk to production environments is limited unless the detailed exception pages are enabled there.
How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:
I don't know
How can this vulnerability be detected on my network or system? Can you suggest some commands?
This vulnerability affects applications using the Action Pack Rubygem on the Rails framework, specifically versions on the 8.1 branch prior to 8.1.2.1, when detailed exception pages are enabled (config.consider_all_requests_local = true). Detection involves verifying the version of the Action Pack gem in use and checking if detailed exception pages are enabled.
To detect the vulnerable version, you can run the following command in your Rails application directory to check the installed version of action_pack:
- bundle list | grep actionpack
Alternatively, you can check the version via RubyGems:
- gem list actionpack
To check if detailed exception pages are enabled, inspect your Rails configuration file (config/environments/development.rb) for the setting:
- config.consider_all_requests_local = true
If both conditions are met (vulnerable version and detailed exception pages enabled), your system is susceptible to this vulnerability.
What immediate steps should I take to mitigate this vulnerability?
The immediate mitigation step is to upgrade the Action Pack gem to version 8.1.2.1 or later, which contains the patch for this vulnerability.
Alternatively, if upgrading is not immediately possible, you can disable detailed exception pages by setting the following configuration in your Rails application environment files (e.g., config/environments/development.rb):
- config.consider_all_requests_local = false
Disabling detailed exception pages will prevent the injection of arbitrary HTML and JavaScript via exception messages, mitigating the XSS risk.