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HIGH

CVE-2025-61921

CVSS v3

7.5

HIGH

EPSS Score

0.5 %

exploit probability, as of 2026-10-19

CISA KEV

No

known exploited

Exploitation

—

SSVC status

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Affected and fixed versions

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • sinatraRubyGemsall versions · fixed in 4.2.0

Vendor advisories

  • CVE-2025-61921 Red Hat Product Security11 known affected

    sinatra: Sinatra has ReDoS vulnerability in ETag header value generation

    3scale-amp2/zync-rhel7 as a component of Red Hat 3scale API Management Platform 2 · 3scale-amp2/zync-rhel8 as a component of Red Hat 3scale API Management Platform 2 · 3scale-amp2/zync-rhel9 as a component of Red Hat 3scale API Management Platform 2

Full record on NVD

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.

Technical details

Published
2025-10-10

Frequently asked questions

What is CVE-2025-61921?

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.

Is CVE-2025-61921 actively exploited?

Active exploitation of CVE-2025-61921 has not been confirmed. Its EPSS score was 0.5% on 2026-10-19, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2025-61921?

CVE-2025-61921 has a CVSS v3 base score of 7.5 (HIGH severity).

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