CVE-2025-61771
published 2025-10-07CVE-2025-61771: Rack is a modular Ruby web server interface. In versions prior to 2.2.19, 3.1.17, and 3.2.2, ``Rack::Multipart::Parser` stores non-file form fields (parts…
PriorityP343high7.5CVSS 3.1
AVNACLPRNUINSUCNINAH
EPSS
0.52%
40.0th percentile
Rack is a modular Ruby web server interface. In versions prior to 2.2.19, 3.1.17, and 3.2.2, ``Rack::Multipart::Parser` stores non-file form fields (parts without a `filename`) entirely in memory as Ruby `String` objects. A single large text field in a multipart/form-data request (hundreds of megabytes or more) can consume equivalent process memory, potentially leading to out-of-memory (OOM) conditions and denial of service (DoS). Attackers can send large non-file fields to trigger excessive memory usage. Impact scales with request size and concurrency, potentially leading to worker crashes or severe garbage-collection overhead. All Rack applications processing multipart form submissions are affected. Versions 2.2.19, 3.1.17, and 3.2.2 enforce a reasonable size cap for non-file fields (e.g., 2 MiB). Workarounds include restricting maximum request body size at the web-server or proxy layer (e.g., Nginx `client_max_body_size`) and validating and rejecting unusually large form fields at the application level.
Affected
9 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| debian | ruby-rack | < ruby-rack 2.2.20-0+deb12u1 (bookworm) | ruby-rack 2.2.20-0+deb12u1 (bookworm) |
| rack | rack | < 2.2.19 | 2.2.19 |
| rack | rack | — | — |
| rack | rack | — | — |
| rack | rack | >= 0 < 2.2.19 | 2.2.19 |
| rack | rack | >= 3.1 < 3.1.17 | 3.1.17 |
| rack | rack | >= 3.1.0 < 3.1.17 | 3.1.17 |
| rack | rack | >= 3.2 < 3.2.2 | 3.2.2 |
| rack | rack | >= 3.2.0 < 3.2.2 | 3.2.2 |
CVSS provenance
nvdv3.17.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
osv7.5HIGH
vendor_debian7.5HIGH
vendor_redhat7.5HIGH
vendor_ubuntu7.5HIGH
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OSV
ruby-rack vulnerabilities
osv·2026-01-14·CVSS 7.5
CVE-2025-59830 [HIGH] ruby-rack vulnerabilities
ruby-rack vulnerabilities
It was discovered that Rack incorrectly handled certain query parameters.
An attacker could possibly use this issue to cause a limited denial of
service. This issue was only addressed in Ubuntu 20.04 LTS and
Ubuntu 22.04 LTS. (CVE-2025-59830)
It was discovered that Rack did not properly handle certain multipart
form data. An attacker could possibly use this issue to cause memory
exhaustion, leading to a denial of service. This issue was only addressed
in Ubuntu 22.04 LTS, Ubuntu 24.04 LTS and Ubuntu 25.10.
(CVE-2025-61770, CVE-2025-61772)
It was discovered that Rack did not properly handle certain form fields.
An attacker could possibly use this issue to cause memory exhaustion,
leading to a denial of service. This issue was only addressed in Ubuntu
22.04 LTS,
GHSA
Rack: Multipart parser buffers large non‑file fields entirely in memory, enabling DoS (memory exhaustion)
ghsa·2025-10-07
CVE-2025-61771 [HIGH] CWE-400 Rack: Multipart parser buffers large non‑file fields entirely in memory, enabling DoS (memory exhaustion)
Rack: Multipart parser buffers large non‑file fields entirely in memory, enabling DoS (memory exhaustion)
## Summary
`Rack::Multipart::Parser` stores non-file form fields (parts without a `filename`) entirely in memory as Ruby `String` objects. A single large text field in a multipart/form-data request (hundreds of megabytes or more) can consume equivalent process memory, potentially leading to out-of-memory (OOM) conditions and denial of service (DoS).
## Details
During multipart parsing, file parts are streamed to temporary files, but non-file parts are buffered into memory:
```ruby
body = String.new # non-file → in-RAM buffer
@mime_parts[mime_index].body << content
```
There is no size limit on these in-memory buffers. As a result, any large text field—while technically valid—will
OSV
Rack: Multipart parser buffers large non‑file fields entirely in memory, enabling DoS (memory exhaustion)
osv·2025-10-07
CVE-2025-61771 [HIGH] Rack: Multipart parser buffers large non‑file fields entirely in memory, enabling DoS (memory exhaustion)
Rack: Multipart parser buffers large non‑file fields entirely in memory, enabling DoS (memory exhaustion)
## Summary
`Rack::Multipart::Parser` stores non-file form fields (parts without a `filename`) entirely in memory as Ruby `String` objects. A single large text field in a multipart/form-data request (hundreds of megabytes or more) can consume equivalent process memory, potentially leading to out-of-memory (OOM) conditions and denial of service (DoS).
## Details
During multipart parsing, file parts are streamed to temporary files, but non-file parts are buffered into memory:
```ruby
body = String.new # non-file → in-RAM buffer
@mime_parts[mime_index].body << content
```
There is no size limit on these in-memory buffers. As a result, any large text field—while technically valid—will
OSV
CVE-2025-61771: Rack is a modular Ruby web server interface
osv·2025-10-07·CVSS 7.5
CVE-2025-61771 [HIGH] CVE-2025-61771: Rack is a modular Ruby web server interface
Rack is a modular Ruby web server interface. In versions prior to 2.2.19, 3.1.17, and 3.2.2, ``Rack::Multipart::Parser` stores non-file form fields (parts without a `filename`) entirely in memory as Ruby `String` objects. A single large text field in a multipart/form-data request (hundreds of megabytes or more) can consume equivalent process memory, potentially leading to out-of-memory (OOM) conditions and denial of service (DoS). Attackers can send large non-file fields to trigger excessive memory usage. Impact scales with request size and concurrency, potentially leading to worker crashes or severe garbage-collection overhead. All Rack applications processing multipart form submissions are affected. Versions 2.2.19, 3.1.17, and 3.2.2 enforce a reasonable size cap for non-file fields (e.g
Ubuntu
Rack vulnerabilities
vendor_ubuntu·2026-01-14·CVSS 7.5
CVE-2025-61771 [HIGH] Rack vulnerabilities
Title: Rack vulnerabilities
Summary: Several security issues were fixed in Rack.
It was discovered that Rack incorrectly handled certain query parameters.
An attacker could possibly use this issue to cause a limited denial of
service. This issue was only addressed in Ubuntu 20.04 LTS and
Ubuntu 22.04 LTS. (CVE-2025-59830)
It was discovered that Rack did not properly handle certain multipart
form data. An attacker could possibly use this issue to cause memory
exhaustion, leading to a denial of service. This issue was only addressed
in Ubuntu 22.04 LTS, Ubuntu 24.04 LTS and Ubuntu 25.10.
(CVE-2025-61770, CVE-2025-61772)
It was discovered that Rack did not properly handle certain form fields.
An attacker could possibly use this issue to cause memory exhaustion,
leading to a denial of serv
Red Hat
rack: Rack's multipart parser buffers large non‑file fields entirely in memory, enabling DoS (memory exhaustion)
vendor_redhat·2025-10-07·CVSS 7.5
CVE-2025-61771 [HIGH] CWE-1284 rack: Rack's multipart parser buffers large non‑file fields entirely in memory, enabling DoS (memory exhaustion)
rack: Rack's multipart parser buffers large non‑file fields entirely in memory, enabling DoS (memory exhaustion)
Rack is a modular Ruby web server interface. In versions prior to 2.2.19, 3.1.17, and 3.2.2, ``Rack::Multipart::Parser` stores non-file form fields (parts without a `filename`) entirely in memory as Ruby `String` objects. A single large text field in a multipart/form-data request (hundreds of megabytes or more) can consume equivalent process memory, potentially leading to out-of-memory (OOM) conditions and denial of service (DoS). Attackers can send large non-file fields to trigger excessive memory usage. Impact scales with request size and concurrency, potentially leading to worker crashes or severe garbage-collection overhead. All Rack applications processing multipart form s
Debian
CVE-2025-61771: ruby-rack - Rack is a modular Ruby web server interface. In versions prior to 2.2.19, 3.1.17...
vendor_debian·2025·CVSS 7.5
CVE-2025-61771 [HIGH] CVE-2025-61771: ruby-rack - Rack is a modular Ruby web server interface. In versions prior to 2.2.19, 3.1.17...
Rack is a modular Ruby web server interface. In versions prior to 2.2.19, 3.1.17, and 3.2.2, ``Rack::Multipart::Parser` stores non-file form fields (parts without a `filename`) entirely in memory as Ruby `String` objects. A single large text field in a multipart/form-data request (hundreds of megabytes or more) can consume equivalent process memory, potentially leading to out-of-memory (OOM) conditions and denial of service (DoS). Attackers can send large non-file fields to trigger excessive memory usage. Impact scales with request size and concurrency, potentially leading to worker crashes or severe garbage-collection overhead. All Rack applications processing multipart form submissions are affected. Versions 2.2.19, 3.1.17, and 3.2.2 enforce a reasonable size cap for non-file fields (e.g
No detection rules found.
No public exploits indexed.
2025-10-07
Published