Summary
Possible ReDoS vulnerability in block_format in Action Mailer
There is a possible ReDoS vulnerability in the block_format helper in Action Mailer. This vulnerability has been assigned the CVE identifier CVE-2024-47889.
Impact
Carefully crafted text can cause the block_format helper to take an unexpected amount of time, possibly resulting in a DoS vulnerability. All users running an affected release should either upgrade or apply the relevant patch immediately.
Ruby 3.2 has mitigations for this problem, so Rails applications using Ruby 3.2 or newer are unaffected. Rails 8.0.0.beta1 requires Ruby 3.2 or greater so is unaffected.
Releases
The fixed releases are available at the normal locations.
Workarounds
Users can avoid calling the block_format helper or upgrade to Ruby 3.2
Credits
Thanks to yuki_osaki for the report!
Impact
A regular expression with worst-case exponential or polynomial matching time is applied to untrusted input, causing excessive CPU use. Typical impact: denial of service when input is crafted to trigger backtracking.
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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actionmailer to 6.1.7.9 or later; actionmailer to 7.0.8.5 or later; actionmailer to 7.1.4.1 or later; actionmailer to 7.2.1.1 or later
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2024-47889? CVE-2024-47889 is a medium-severity inefficient regular expression (ReDoS) vulnerability in actionmailer (rubygems), affecting versions >= 3.0.0, < 6.1.7.9. It is fixed in 6.1.7.9, 7.0.8.5, 7.1.4.1, 7.2.1.1. A regular expression with worst-case exponential or polynomial matching time is applied to untrusted input, causing excessive CPU use.
- Which versions of actionmailer are affected by CVE-2024-47889? actionmailer (rubygems) versions >= 3.0.0, < 6.1.7.9 is affected.
- Is there a fix for CVE-2024-47889? Yes. CVE-2024-47889 is fixed in 6.1.7.9, 7.0.8.5, 7.1.4.1, 7.2.1.1. Upgrade to this version or later.
- Is CVE-2024-47889 exploitable, and should I be worried? Whether CVE-2024-47889 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-2024-47889 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-2024-47889?
- Upgrade
actionmailerto 6.1.7.9 or later - Upgrade
actionmailerto 7.0.8.5 or later - Upgrade
actionmailerto 7.1.4.1 or later - Upgrade
actionmailerto 7.2.1.1 or later
- Upgrade