CVE-2025-61772: Rack Denial of Service Vulnerability

HIGH
Advisory Identifier: GHSA-wpv5-97wm-hp9c
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CVSS 7.5
CWE-400
Published
Advisory Summary

CVE-2025-61772 is a HIGH (CVSS 7.5) denial of service vulnerability (CWE-400: Uncontrolled Resource Consumption) affecting Rack libraries in the RubyGems ecosystem. The issue involves rack's multipart parser buffers unbounded per-part headers, enabling dos (memory exhaustion). Remediation is available by upgrading affected packages to version 2.2.19, 3.1.17, 3.2.2.

CVE-2025-61772 at a Glance

CVE Identifier CVE-2025-61772
GHSA Identifier GHSA-wpv5-97wm-hp9c
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-400: Uncontrolled Resource Consumption
Affected Product Rack
Package Ecosystem RubyGems
Published Date
Last Updated

Security Impact

CVSS: 7.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity None (I:N)
Availability High (A:H)

How to Fix CVE-2025-61772

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

rack fixed: 2.2.19 
Upgrade rack to 2.2.19
rack fixed: 3.1.17 
Upgrade rack to 3.1.17
rack fixed: 3.2.2 
Upgrade rack to 3.2.2
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 rack

How to Check if You Are Affected

To determine whether your application is affected by CVE-2025-61772, inspect your project dependencies for Rack:

inspect dependencies for rack

Analyze the terminal output to locate any version of Rack in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.2.19), 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-400: Uncontrolled Resource Consumption, where the product does not properly control the allocation and maintenance of a limited resource. In Rack, 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

## Summary `Rack::Multipart::Parser` can accumulate unbounded data when a multipart part’s header block never terminates with the required blank line (`CRLFCRLF`). The parser keeps appending incoming bytes to memory without a size cap, allowing a remote attacker to exhaust memory and cause a denial of service (DoS). ## Details While reading multipart headers, the parser waits for `CRLFCRLF` using: ```ruby @sbuf.scan_until(/(.*?\r\n)\r\n/m) ``` If the terminator never appears, it continues appending data (`@sbuf.concat(content)`) indefinitely. There is no limit on accumulated header bytes, so a single malformed part can consume memory proportional to the request body size. ## Impact Attackers can send incomplete multipart headers to trigger high memory use, leading to process termination (OOM) or severe slowdown. The effect scales with request size limits and concurrency. All applications handling multipart uploads may be affected. ## Mitigation * Upgrade to a patched Rack version that caps per-part header size (e.g., 64 KiB). * Until then, restrict maximum request sizes at the proxy or web server layer (e.g., Nginx `client_max_body_size`).

CVE-2025-61772 Affected Rack Versions

3 component(s)
Fixed Versions:
2.2.193.1.173.2.2
Product / Package Ecosystem Affected Versions Fixed Version
rack
gem/rack
RubyGems
< 2.2.19
2.2.19
rack
gem/rack
RubyGems
≥ 3.1
< 3.1.17
3.1.17
rack
gem/rack
RubyGems
≥ 3.2
< 3.2.2
3.2.2

References

GitHub Advisory / Wiki ADVISORY
https://github.com/rack/rack/security/advisories/GHSA-wpv5-97wm-hp9c
NVD — CVE-2025-61772 NVD
https://nvd.nist.gov/vuln/detail/CVE-2025-61772
Security Fix Commit FIX COMMIT
https://github.com/rack/rack/commit/589127f4ac8b5cf11cf88fb0cd116ffed4d2181e
Security Fix Commit FIX COMMIT
https://github.com/rack/rack/commit/d869fed663b113b95a74ad53e1b5cae6ab31f29e
Security Fix Commit FIX COMMIT
https://github.com/rack/rack/commit/e08f78c656c9394d6737c022bde087e0f33336fd
Rack Source Repository REPOSITORY
https://github.com/rack/rack
Rack Source Repository REPOSITORY
https://github.com/rubysec/ruby-advisory-db/blob/master/gems/rack/CVE-2025-61772.yml

Frequently Asked Questions

What is CVE-2025-61772?
CVE-2025-61772 is a security vulnerability in Rack involving Rack's multipart parser buffers unbounded per-part headers, enabling DoS (memory exhaustion) under CWE-400: Uncontrolled Resource Consumption.
Which Rack versions are affected?
Affected versions include releases prior to 2.2.19, 3.1.17, 3.2.2 across affected packages: rack.
What version fixes CVE-2025-61772?
Upgrading to 2.2.19, 3.1.17, 3.2.2 (or the latest patched release for your respective branch) resolves the vulnerability.
Is rack affected?
Yes, rack is affected in releases prior to 2.2.19, 3.1.17, 3.2.2. Upgrade your dependency to 2.2.19, 3.1.17, 3.2.2 or later.
What is the CVSS score of CVE-2025-61772?
CVE-2025-61772 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2025-61772?
CVE-2025-61772 is classified under CWE-400: Uncontrolled Resource Consumption (The product does not properly control the allocation and maintenance of a limited resource.).
How can I check RubyGems dependencies for CVE-2025-61772?
Run the dependency tree command: 'inspect dependencies for rack'. 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-wpv5-97wm-hp9c",
  "modified" : "2025-10-13T15:30:01Z",
  "published" : "2025-10-07T17:28:06Z",
  "aliases" : [ "CVE-2025-61772" ],
  "summary" : "Rack's multipart parser buffers unbounded per-part headers, enabling DoS (memory exhaustion)",
  "details" : "## Summary\n\n`Rack::Multipart::Parser` can accumulate unbounded data when a multipart part’s header block never terminates with the required blank line (`CRLFCRLF`). The parser keeps appending incoming bytes to memory without a size cap, allowing a remote attacker to exhaust memory and cause a denial of service (DoS).\n\n## Details\n\nWhile reading multipart headers, the parser waits for `CRLFCRLF` using:\n\n```ruby\n@sbuf.scan_until(/(.*?\\r\\n)\\r\\n/m)\n```\n\nIf the terminator never appears, it continues appending data (`@sbuf.concat(content)`) indefinitely. There is no limit on accumulated header bytes, so a single malformed part can consume memory proportional to the request body size.\n\n## Impact\n\nAttackers can send incomplete multipart headers to trigger high memory use, leading to process termination (OOM) or severe slowdown. The effect scales with request size limits and concurrency. All applications handling multipart uploads may be affected.\n\n## Mitigation\n\n* Upgrade to a patched Rack version that caps per-part header size (e.g., 64 KiB).\n* Until then, restrict maximum request sizes at the proxy or web server layer (e.g., Nginx `client_max_body_size`).",
  "severity" : [ {
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    "url" : "https://github.com/rack/rack/commit/589127f4ac8b5cf11cf88fb0cd116ffed4d2181e"
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    "url" : "https://github.com/rack/rack/commit/d869fed663b113b95a74ad53e1b5cae6ab31f29e"
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    "url" : "https://github.com/rack/rack/commit/e08f78c656c9394d6737c022bde087e0f33336fd"
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    "type" : "PACKAGE",
    "url" : "https://github.com/rack/rack"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rubysec/ruby-advisory-db/blob/master/gems/rack/CVE-2025-61772.yml"
  } ],
  "database_specific" : {
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    "github_reviewed_at" : "2025-10-07T17:28:06Z",
    "nvd_published_at" : "2025-10-07T15:16:03Z"
  }
}