Sinatra has ReDoS vulnerability in ETag header value generation
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.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2025-61921
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 2 Nov 2026, 18:25 UTC · Revision 1
Source evidence
Sinatra has ReDoS vulnerability in ETag header value generation
core-osv · Original sourcePublished 10 Oct 2025, 19:28 UTC
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.
osv:CVE-2025-61921
Complete source record
{
"id": "804676ac0a5a1bb42cb86df2029b5491c84ae15a5f43f780c4ad8b2ef630c047",
"url": "https://osv.dev/vulnerability/CVE-2025-61921",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "Sinatra has ReDoS vulnerability in ETag header value generation",
"summary": "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.",
"evidence": "osv:CVE-2025-61921",
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"aliases": [
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"metrics": [
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"type": "CVSS_V4",
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U"
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"type": "GIT",
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"cpe": "cpe:2.3:a:sinatrarb:sinatra:*:*:*:*:*:*:*:*",
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"database_specific": {
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"modified": "2026-10-28T02:30:22.039876149Z",
"provider": "osv",
"references": [
"https://bugs.ruby-lang.org/issues/19104",
"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/61xxx/CVE-2025-61921.json",
"https://github.com/sinatra/sinatra/security/advisories/GHSA-mr3q-g2mv-mr4q",
"https://nvd.nist.gov/vuln/detail/CVE-2025-61921",
"https://github.com/sinatra/sinatra/issues/2120",
"https://github.com/sinatra/sinatra/pull/1823",
"https://github.com/sinatra/sinatra/pull/2121"
],
"provider_metadata": {
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"evidence": "/id"
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"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 488350,
"published_at": "2025-10-10T19:28:10.688+00:00"
}