Summary
CSRF Vulnerability in rails-ujs
There is a vulnerability in rails-ujs that allows attackers to send CSRF tokens to wrong domains.
Versions Affected: rails <= 6.0.3
Not affected: Applications which don't use rails-ujs.
Fixed Versions: rails >= 5.2.4.3, rails >= 6.0.3.1
Impact
This is a regression of CVE-2015-1840.
In the scenario where an attacker might be able to control the href attribute of an anchor tag or the action attribute of a form tag that will trigger a POST action, the attacker can set the href or action to a cross-origin URL, and the CSRF token will be sent.
Workarounds
To work around this problem, change code that allows users to control the href attribute of an anchor tag or the action attribute of a form tag to filter the user parameters.
For example, code like this:
link_to params
to code like this:
link_to filtered_params
def filtered_params
# Filter just the parameters that you trust
end
Impact
A victim's authenticated browser session is used to submit forged requests to an application that cannot distinguish them from legitimate ones. Typical impact: state-changing actions performed as the victim without their consent.
CVE-2020-8167 has a CVSS score of 6.5 (Medium). The vector is network-reachable, no privileges required, and user interaction required. 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 (5.2.4.3, 6.0.3.1); 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.
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See it in your environmentNew to Kodem? Get a demo →Remediation advice
actionview to 5.2.4.3 or later; actionview to 6.0.3.1 or later
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2020-8167? CVE-2020-8167 is a medium-severity cross-site request forgery (CSRF) vulnerability in actionview (rubygems), affecting versions >= 5.0.0, <= 5.2.4.2. It is fixed in 5.2.4.3, 6.0.3.1. A victim's authenticated browser session is used to submit forged requests to an application that cannot distinguish them from legitimate ones.
- How severe is CVE-2020-8167? CVE-2020-8167 has a CVSS score of 6.5 (Medium). 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 actionview are affected by CVE-2020-8167? actionview (rubygems) versions >= 5.0.0, <= 5.2.4.2 is affected.
- Is there a fix for CVE-2020-8167? Yes. CVE-2020-8167 is fixed in 5.2.4.3, 6.0.3.1. Upgrade to this version or later.
- Is CVE-2020-8167 exploitable, and should I be worried? Whether CVE-2020-8167 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-2020-8167 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-2020-8167?
- Upgrade
actionviewto 5.2.4.3 or later - Upgrade
actionviewto 6.0.3.1 or later
- Upgrade