CVE-2026-33658: Rails Active Storage DoS Vulnerability via Multi-Range Requests
Summary
CVE-2026-33658: Rails Active Storage has a possible DoS vulnerability in proxy mode via multi-range requests. Affects activestorage across 3 version ranges.
< 7.2.3.1
>= 8.0.0, < 8.0.4.1
>= 8.1.0, < 8.1.2.1
Fixed in 7.2.3.1, 8.0.4.1 or 8.1.2.1, depending on the release line you run. How to fix ↓
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Background
Rails Active Storage is a component of the Ruby on Rails framework that facilitates file uploads and management. It allows developers to store files on cloud services or local storage, providing a seamless interface for handling file attachments in applications. However, Active Storage has a vulnerability that can be exploited through crafted HTTP requests, leading to potential denial of service (DoS) conditions.
Vulnerability Detail
The vulnerability arises from Active Storage's proxy controller, which does not impose limits on the number of byte ranges specified in an HTTP Range header. An attacker can exploit this by sending requests with thousands of small byte ranges, which leads to excessive CPU usage compared to standard file requests. This disproportionate resource consumption can result in a denial of service, affecting the availability of the application.
How To Fix
Latest published version: 8.1.4 as of 22 Oct 2026
gem install activestorage -v 8.1.4Upgrading to it may include breaking changes; the versions below are the minimum fixed release for this vulnerability.
If you can't move to the latest
The minimum fixed version depends on the release line you run.
-
< 7.2.3.17.2.3.1gem install activestorage -v 7.2.3.1 -
>= 8.0.0, < 8.0.4.18.0.4.1gem install activestorage -v 8.0.4.1 -
>= 8.1.0, < 8.1.2.18.1.2.1gem install activestorage -v 8.1.2.1
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Workaround
As a temporary workaround, you can implement rate limiting on your server to restrict the number of requests that can be processed in a given time frame. This can help mitigate the impact of the vulnerability until a proper fix is applied.
Conclusion
The Rails Active Storage vulnerability (CVE-2026-33658) presents a risk of denial of service through crafted multi-range requests. It is crucial for developers using affected versions to update their packages promptly and consider implementing workarounds to protect their applications.
See every vulnerability recorded for activestorage →
FAQ
The vulnerability allows an attacker to exploit the Active Storage proxy controller by sending requests with excessive byte ranges, leading to high CPU usage and potential denial of service.
Versions 8.0.0 to 8.1.2.1, and 7.2.3.1 and earlier are affected by this vulnerability.
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The CVSS score for this vulnerability is 2.3, indicating a low severity level.
If immediate updates are not possible, implement rate limiting on your server to mitigate the risk of denial of service until you can apply the patch.
References
Related vulnerabilities
Recent vulnerabilities recorded for activestorage.
