CVE-2025-61921 – Sinatra has ReDoS vulnerability in ETag header value generation

CVE ID : CVE-2025-61921

Published : Oct. 10, 2025, 8:15 p.m. | 23 minutes ago

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.

Severity: 2.7 | LOW

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