Summary
Action Pack contains Information Disclosure / Unintended Method Execution vulnerability
Impact
There is a possible information disclosure / unintended method execution vulnerability in Action Pack when using the redirect_to or polymorphic_url helper with untrusted user input.
Vulnerable code will look like this.
redirect_to(params[:some_param])
All users running an affected release should either upgrade or use one of the workarounds immediately.
Releases
The FIXED releases are available at the normal locations.
Workarounds
To work around this problem, it is recommended to use an allow list for valid parameters passed from the user. For example,
private def check(param)
case param
when "valid"
param
else
"/"
end
end
def index
redirect_to(check(params[:some_param]))
end
Or force the user input to be cast to a string like this,
def index
redirect_to(params[:some_param].to_s)
end
Patches
To aid users who aren't able to upgrade immediately we have provided patches for the two supported release series. They are in git-am format and consist of a single changeset.
- 5-2-information-disclosure.patch - Patch for 5.2 series
- 6-0-information-disclosure.patch - Patch for 6.0 series
- 6-1-information-disclosure.patch - Patch for 6.1 series
Please note that only the 5.2, 6.0, and 6.1 series are supported at present. Users of earlier unsupported releases are advised to upgrade as soon as possible as we cannot guarantee the continued availability of security fixes for unsupported releases.
Credits
Thanks to Benoit Côté-Jodoin from Shopify for reporting this.
Impact
CVE-2021-22885 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (6.0.3.7, 6.1.3.2, 5.2.6, 5.2.4.6); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Already deployed Kodem?
See it in your environmentNew to Kodem? Get a demo →Remediation advice
actionpack to 6.0.3.7 or later; actionpack to 6.1.3.2 or later; actionpack to 5.2.6 or later; actionpack to 5.2.4.6 or later
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2021-22885? CVE-2021-22885 is a high-severity security vulnerability in actionpack (rubygems), affecting versions >= 6.0.0, <= 6.0.3.6. It is fixed in 6.0.3.7, 6.1.3.2, 5.2.6, 5.2.4.6.
- How severe is CVE-2021-22885? CVE-2021-22885 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of actionpack are affected by CVE-2021-22885? actionpack (rubygems) versions >= 6.0.0, <= 6.0.3.6 is affected.
- Is there a fix for CVE-2021-22885? Yes. CVE-2021-22885 is fixed in 6.0.3.7, 6.1.3.2, 5.2.6, 5.2.4.6. Upgrade to this version or later.
- Is CVE-2021-22885 exploitable, and should I be worried? Whether CVE-2021-22885 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2021-22885 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2021-22885?
- Upgrade
actionpackto 6.0.3.7 or later - Upgrade
actionpackto 6.1.3.2 or later - Upgrade
actionpackto 5.2.6 or later - Upgrade
actionpackto 5.2.4.6 or later
- Upgrade