{"id":"CVE-2026-73495","state":"PUBLISHED","title":"blaze: Chunked-body trailer fields promoted into Request.headers in blaze-server (front-end header-sanitization bypass)","description":"blaze is a Scala library for building asynchronous pipelines, with a focus on network IO. Prior to 0.23.18 and 1.0.0-M42, blaze-server can merge HTTP/1.1 chunked-body trailer fields into Request.headers. Because trailer fields are attacker-controlled, an unauthenticated remote client can inject arbitrary header names and values, including X-Forwarded-For and internal authorization headers, that a fronting proxy sanitized from the request-header section, bypassing header-based trust decisions in the application. Any http4s application using BlazeServerBuilder over HTTP/1.1 whose routes or middleware trust proxy-set headers, including X-Forwarded-For, X-Real-IP, and X-Forwarded-Host, is affected. If a fronting proxy strips or normalizes those headers but forwards chunked bodies with trailers intact, an attacker can spoof client IP for allow-lists, rate limits, or auditing, forge the https scheme, or inject internal authorization headers. A promoted Connection: close trailer is also honored, allowing attacker-controlled termination of pooled backend connections. This issue is fixed in versions 0.23.18 and 1.0.0-M42.","publishedAt":"2026-08-12T21:11:55.180Z","updatedAt":"2026-08-13T13:04:05.574Z","severity":{"score":7.4,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N","source":"GitHub_M"},"assigner":"GitHub_M","products":["http4s blaze"],"affected":[{"vendor":"http4s","product":"blaze","versions":[{"version":"< 0.23.18","status":"affected"},{"version":">= 1.0.0-M1, < 1.0.0-M42","status":"affected"}]}],"references":["https://github.com/http4s/blaze/security/advisories/GHSA-46q4-43ph-c6fr","https://github.com/http4s/blaze/commit/ef3e666c146cfc16cb6603f1fc3c464daab4a24f","https://github.com/http4s/blaze/releases/tag/v0.23.18","https://github.com/http4s/blaze/releases/tag/v1.0.0-M42"],"weaknesses":["CWE-444"],"ingestedAt":"2026-10-29T20:12:58.252Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/73xxx/CVE-2026-73495.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-73495","state":"PUBLISHED","datePublished":"2026-08-12T21:11:55.180Z","dateUpdated":"2026-08-13T13:04:05.574Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-08-12T19:00:33.735Z"},"containers":{"cna":{"title":"blaze: Chunked-body trailer fields promoted into Request.headers in blaze-server (front-end header-sanitization bypass)","descriptions":[{"lang":"en","value":"blaze is a Scala library for building asynchronous pipelines, with a focus on network IO. Prior to 0.23.18 and 1.0.0-M42, blaze-server can merge HTTP/1.1 chunked-body trailer fields into Request.headers. Because trailer fields are attacker-controlled, an unauthenticated remote client can inject arbitrary header names and values, including X-Forwarded-For and internal authorization headers, that a fronting proxy sanitized from the request-header section, bypassing header-based trust decisions in the application. Any http4s application using BlazeServerBuilder over HTTP/1.1 whose routes or middleware trust proxy-set headers, including X-Forwarded-For, X-Real-IP, and X-Forwarded-Host, is affected. If a fronting proxy strips or normalizes those headers but forwards chunked bodies with trailers intact, an attacker can spoof client IP for allow-lists, rate limits, or auditing, forge the https scheme, or inject internal authorization headers. A promoted Connection: close trailer is also honored, allowing attacker-controlled termination of pooled backend connections. This issue is fixed in versions 0.23.18 and 1.0.0-M42."}],"affected":[{"vendor":"http4s","product":"blaze","versions":[{"version":"< 0.23.18","status":"affected"},{"version":">= 1.0.0-M1, < 1.0.0-M42","status":"affected"}]}],"references":[{"url":"https://github.com/http4s/blaze/security/advisories/GHSA-46q4-43ph-c6fr","name":"https://github.com/http4s/blaze/security/advisories/GHSA-46q4-43ph-c6fr","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/http4s/blaze/commit/ef3e666c146cfc16cb6603f1fc3c464daab4a24f","name":"https://github.com/http4s/blaze/commit/ef3e666c146cfc16cb6603f1fc3c464daab4a24f","tags":["x_refsource_MISC"]},{"url":"https://github.com/http4s/blaze/releases/tag/v0.23.18","name":"https://github.com/http4s/blaze/releases/tag/v0.23.18","tags":["x_refsource_MISC"]},{"url":"https://github.com/http4s/blaze/releases/tag/v1.0.0-M42","name":"https://github.com/http4s/blaze/releases/tag/v1.0.0-M42","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"HIGH","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":7.4,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-444","lang":"en","description":"CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-08-12T21:11:55.180Z"},"source":{"advisory":"GHSA-46q4-43ph-c6fr","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-08-13T13:02:55.958244Z","id":"CVE-2026-73495","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-08-13T13:04:05.574Z"}}]}}}