Summary
Rails Active Storage has a possible DoS vulnerability when in proxy mode via Range requests
Releases
The fixed releases are available at the normal locations.
Credit
This issue was responsibly reported by Hackerone user pirikara
Impact
When serving files through Active Storage's Blobs::ProxyController, the controller loads the entire requested byte range into memory before sending it. A request with a large or unbounded Range header (e.g. bytes=0-) could cause the server to allocate memory proportional to the file size, possibly resulting in a DoS vulnerability through memory exhaustion.
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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activestorage to 8.1.2.1 or later; activestorage to 8.0.4.1 or later; activestorage to 7.2.3.1 or later
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2026-33174? CVE-2026-33174 is a medium-severity security vulnerability in activestorage (rubygems), affecting versions >= 8.1.0.beta1, < 8.1.2.1. It is fixed in 8.1.2.1, 8.0.4.1, 7.2.3.1.
- Which versions of activestorage are affected by CVE-2026-33174? activestorage (rubygems) versions >= 8.1.0.beta1, < 8.1.2.1 is affected.
- Is there a fix for CVE-2026-33174? Yes. CVE-2026-33174 is fixed in 8.1.2.1, 8.0.4.1, 7.2.3.1. Upgrade to this version or later.
- Is CVE-2026-33174 exploitable, and should I be worried? Whether CVE-2026-33174 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-2026-33174 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-2026-33174?
- Upgrade
activestorageto 8.1.2.1 or later - Upgrade
activestorageto 8.0.4.1 or later - Upgrade
activestorageto 7.2.3.1 or later
- Upgrade