# CVE-2025-61921: ruby-sinatra: Sinatra is a domain-specific language for creating web applications in Ruby

CVE-2025-61921 is fixed in 3 products on 1 platform, first by ruby-rack-protection 2.0.8.1-2+deb11u1ubuntu0.1~esm1, released October 10, 2025. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2025-61921
- Priority: High
- CVSS: 7.5 (Medium)
- EPSS: 0.0050
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Oct 10, 2025

## Description

Sinatra is a domain-specific language for creating web applications in Ruby. In versions prior to 4.2.0, there is a denial of service vulnerability in the `If-Match` and `If-None-Match` header parsing component of Sinatra, if the `etag` method is used when constructing the response. Carefully crafted input can cause `If-Match` and `If-None-Match` header parsing in Sinatra to take an unexpected amount of time, possibly resulting in a denial of service attack vector. This header is typically involved in generating the `ETag` header value. Any applications that use the `etag` method when generating a response are impacted. Version 4.2.0 fixes the issue.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | ruby-rack-protection Ubuntu 22.04.1 LTS (jammy) | 2.0.8.1-2+deb11u1ubuntu0.1~esm1 | [ruby-rack-protection 2.0.8.1-2+deb11u1ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-ruby-rack-protection-2.0.8.1-2-deb11u1ubuntu0.1-esm1.md) | Oct 10, 2025 |
| Linux | ruby-rack-protection Ubuntu 26.04.1 LTS (resolute) | 4.2.1-1 | [ruby-rack-protection 4.2.1-1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-ruby-rack-protection-4.2.1-1.md) | Oct 10, 2025 |
| Linux | ruby-sinatra Debian 12.15 (bookworm) | 3.0.5-3+deb12u1 | [DEBIAN-CVE-2025-61921](https://patchblox.com/security/data/fix/linux/debian-cve-2025-61921.md) | Oct 10, 2025 |
| Linux | ruby-sinatra Debian 14 | 4.2.1-1 | [DEBIAN-CVE-2025-61921](https://patchblox.com/security/data/fix/linux/debian-cve-2025-61921.md) | Oct 10, 2025 |
| Linux | ruby-sinatra Ubuntu 18.04.6 LTS (bionic) | 1.4.8-1ubuntu0.1~esm3 | [ruby-sinatra 1.4.8-1ubuntu0.1~esm3](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-ruby-sinatra-1.4.8-1ubuntu0.1-esm3.md) | Oct 10, 2025 |
| Linux | ruby-sinatra Ubuntu 22.04.1 LTS (jammy) | 2.0.8.1-2+deb11u1ubuntu0.1~esm1 | [ruby-sinatra 2.0.8.1-2+deb11u1ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-ruby-sinatra-2.0.8.1-2-deb11u1ubuntu0.1-esm1.md) | Oct 10, 2025 |
| Linux | ruby-sinatra Ubuntu 26.04.1 LTS (resolute) | 4.2.1-1 | [ruby-sinatra 4.2.1-1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-ruby-sinatra-4.2.1-1.md) | Oct 10, 2025 |
| Linux | ruby-sinatra-contrib Ubuntu 22.04.1 LTS (jammy) | 2.0.8.1-2+deb11u1ubuntu0.1~esm1 | [ruby-sinatra-contrib 2.0.8.1-2+deb11u1ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-ruby-sinatra-contrib-2.0.8.1-2-deb11u1ubuntu0.1-esm1.md) | Oct 10, 2025 |
| Linux | ruby-sinatra-contrib Ubuntu 26.04.1 LTS (resolute) | 4.2.1-1 | [ruby-sinatra-contrib 4.2.1-1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-ruby-sinatra-contrib-4.2.1-1.md) | Oct 10, 2025 |

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Data as of 2026-11-10T13:56:55Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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