CVE-2026-33174: Activestorage Denial of Service Vulnerability

MODERATE
Advisory Identifier: GHSA-r46p-8f7g-vvvg
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CWE-789
Published
Advisory Summary

CVE-2026-33174 is a MODERATE denial of service vulnerability (CWE-789: Memory Allocation with Excessive Size Value) affecting Activestorage libraries in the RubyGems ecosystem. The issue involves rails active storage has a possible dos vulnerability when in proxy mode via range requests. Remediation is available by upgrading affected packages to version 8.1.2.1, 8.0.4.1, 7.2.3.1.

CVE-2026-33174 at a Glance

CVE Identifier CVE-2026-33174
GHSA Identifier GHSA-r46p-8f7g-vvvg
Severity MODERATE
CVSS v3.1 Base Score N/A
CWE Classification CWE-789: Memory Allocation with Excessive Size Value
Affected Product Activestorage
Package Ecosystem RubyGems
Published Date
Last Updated

How to Fix CVE-2026-33174

To remediate this vulnerability, upgrade all affected Activestorage dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

activestorage fixed: 8.1.2.1 
Upgrade activestorage to 8.1.2.1
activestorage fixed: 8.0.4.1 
Upgrade activestorage to 8.0.4.1
activestorage fixed: 7.2.3.1 
Upgrade activestorage to 7.2.3.1
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for activestorage

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-33174, inspect your project dependencies for Activestorage:

inspect dependencies for activestorage

Analyze the terminal output to locate any version of Activestorage in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 8.1.2.1), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-789: Memory Allocation with Excessive Size Value, where the product allocates memory based on an untrusted, large size value, but it does not ensure that the size is within expected limits, allowing arbitrary amounts of memory to be allocated. In Activestorage, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### 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. ### Releases The fixed releases are available at the normal locations. ### Credit This issue was responsibly reported by Hackerone user [pirikara](https://hackerone.com/pirikara)

CVE-2026-33174 Affected Activestorage Versions

3 component(s)
Fixed Versions:
8.1.2.18.0.4.17.2.3.1
Product / Package Ecosystem Affected Versions Fixed Version
activestorage
gem/activestorage
RubyGems
≥ 8.1.0.beta1
< 8.1.2.1
8.1.2.1
activestorage
gem/activestorage
RubyGems
≥ 8.0.0.beta1
< 8.0.4.1
8.0.4.1
activestorage
gem/activestorage
RubyGems
< 7.2.3.1
7.2.3.1

References

GitHub Advisory / Wiki ADVISORY
https://github.com/rails/rails/security/advisories/GHSA-r46p-8f7g-vvvg
NVD — CVE-2026-33174 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-33174
Security Fix Commit FIX COMMIT
https://github.com/rails/rails/commit/2cd933c366b777f873d4d590127da2f4a25e4ba5
Security Fix Commit FIX COMMIT
https://github.com/rails/rails/commit/42012eaaa88dfc7d0030161b2bc8074a7bbce92a
Security Fix Commit FIX COMMIT
https://github.com/rails/rails/commit/8159a9c3de3f27a2bcf2866b8bf9ceb9075e229b
Activestorage Source Repository REPOSITORY
https://github.com/rails/rails
Activestorage Release RELEASE
https://github.com/rails/rails/releases/tag/v7.2.3.1
Activestorage Release RELEASE
https://github.com/rails/rails/releases/tag/v8.0.4.1
Activestorage Release RELEASE
https://github.com/rails/rails/releases/tag/v8.1.2.1
Activestorage Source Repository REPOSITORY
https://github.com/rubysec/ruby-advisory-db/blob/master/gems/activestorage/CVE-2026-33174.yml

Frequently Asked Questions

What is CVE-2026-33174?
CVE-2026-33174 is a security vulnerability in Activestorage involving Rails Active Storage has a possible DoS vulnerability when in proxy mode via Range requests under CWE-789: Memory Allocation with Excessive Size Value.
Which Activestorage versions are affected?
Affected versions include releases prior to 8.1.2.1, 8.0.4.1, 7.2.3.1 across affected packages: activestorage.
What version fixes CVE-2026-33174?
Upgrading to 8.1.2.1, 8.0.4.1, 7.2.3.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is activestorage affected?
Yes, activestorage is affected in releases prior to 8.1.2.1, 8.0.4.1, 7.2.3.1. Upgrade your dependency to 8.1.2.1, 8.0.4.1, 7.2.3.1 or later.
What CWE is associated with CVE-2026-33174?
CVE-2026-33174 is classified under CWE-789: Memory Allocation with Excessive Size Value (The product allocates memory based on an untrusted, large size value, but it does not ensure that the size is within expected limits, allowing arbitrary amounts of memory to be allocated.).
How can I check RubyGems dependencies for CVE-2026-33174?
Run the dependency tree command: 'inspect dependencies for activestorage'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-r46p-8f7g-vvvg",
  "modified" : "2026-05-13T16:16:08Z",
  "published" : "2026-03-23T21:08:54Z",
  "aliases" : [ "CVE-2026-33174" ],
  "summary" : "Rails Active Storage has a possible DoS vulnerability when in proxy mode via Range requests",
  "details" : "### Impact\nWhen 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.\n\n### Releases\nThe fixed releases are available at the normal locations.\n\n### Credit\nThis issue was responsibly reported by Hackerone user [pirikara](https://hackerone.com/pirikara)",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "RubyGems",
      "name" : "activestorage"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "8.1.0.beta1"
      }, {
        "fixed" : "8.1.2.1"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "RubyGems",
      "name" : "activestorage"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "8.0.0.beta1"
      }, {
        "fixed" : "8.0.4.1"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "RubyGems",
      "name" : "activestorage"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "7.2.3.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/rails/rails/security/advisories/GHSA-r46p-8f7g-vvvg"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-33174"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rails/rails/commit/2cd933c366b777f873d4d590127da2f4a25e4ba5"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rails/rails/commit/42012eaaa88dfc7d0030161b2bc8074a7bbce92a"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rails/rails/commit/8159a9c3de3f27a2bcf2866b8bf9ceb9075e229b"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/rails/rails"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rails/rails/releases/tag/v7.2.3.1"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rails/rails/releases/tag/v8.0.4.1"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rails/rails/releases/tag/v8.1.2.1"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rubysec/ruby-advisory-db/blob/master/gems/activestorage/CVE-2026-33174.yml"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-789" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-23T21:08:54Z",
    "nvd_published_at" : "2026-03-24T00:16:28Z"
  }
}