CVE-2025-61921Sinatra is a domain-specific language for creating web applications in Ruby.
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No exploitation reported and no EPSS estimate yet.
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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.
- CVSS
- 7.5 HIGH (v3.1, NVD)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Weakness (CWE)
- CWE-1333
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Not given
- NVD analysis
- Analyzed
- Record last updated
- Jun 17, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
sinatrarb sinatra sinatrarb:sinatra | before 4.2.0 | NVD |
References
- https://bugs.ruby-lang.org/issues/19104issue-tracking
- https://github.com/sinatra/sinatra/issues/2120issue-tracking
- https://github.com/sinatra/sinatra/pull/1823exploit, patch
- https://github.com/sinatra/sinatra/pull/2121patch
- https://github.com/sinatra/sinatra/security/advisories/GHSA-mr3q-g2mv-mr4qvendor-advisory
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.