CVE-2025-61772: Rack Denial of Service Vulnerability
HIGHCVE-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
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).
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.
Upgrade rack to 2.2.19Upgrade rack to 3.1.17Upgrade rack to 3.2.2Run the following command in your project directory to verify that all resolved dependencies use the patched release:
inspect dependencies for rackHow 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 rackAnalyze 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
CVE-2025-61772 Affected Rack Versions
3 component(s)References
Frequently Asked Questions
What is CVE-2025-61772?
Which Rack versions are affected?
What version fixes CVE-2025-61772?
Is rack affected?
What is the CVSS score of CVE-2025-61772?
What CWE is associated with CVE-2025-61772?
How can I check RubyGems dependencies for CVE-2025-61772?
Machine-readable OSV JSON
OSV v1.5 Schema
{
"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" : [ {
"type" : "CVSS_V3",
"score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
} ],
"affected" : [ {
"package" : {
"ecosystem" : "RubyGems",
"name" : "rack"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "0"
}, {
"fixed" : "2.2.19"
} ]
} ]
}, {
"package" : {
"ecosystem" : "RubyGems",
"name" : "rack"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "3.1"
}, {
"fixed" : "3.1.17"
} ]
} ]
}, {
"package" : {
"ecosystem" : "RubyGems",
"name" : "rack"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "3.2"
}, {
"fixed" : "3.2.2"
} ]
} ]
} ],
"references" : [ {
"type" : "WEB",
"url" : "https://github.com/rack/rack/security/advisories/GHSA-wpv5-97wm-hp9c"
}, {
"type" : "ADVISORY",
"url" : "https://nvd.nist.gov/vuln/detail/CVE-2025-61772"
}, {
"type" : "WEB",
"url" : "https://github.com/rack/rack/commit/589127f4ac8b5cf11cf88fb0cd116ffed4d2181e"
}, {
"type" : "WEB",
"url" : "https://github.com/rack/rack/commit/d869fed663b113b95a74ad53e1b5cae6ab31f29e"
}, {
"type" : "WEB",
"url" : "https://github.com/rack/rack/commit/e08f78c656c9394d6737c022bde087e0f33336fd"
}, {
"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" : {
"cwe_ids" : [ "CWE-400" ],
"severity" : "HIGH",
"github_reviewed" : true,
"github_reviewed_at" : "2025-10-07T17:28:06Z",
"nvd_published_at" : "2025-10-07T15:16:03Z"
}
}