{"id":"CVE-2026-73495","summary":"blaze: Chunked-body trailer fields promoted into Request.headers in blaze-server (front-end header-sanitization bypass)","details":"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.","aliases":["GHSA-46q4-43ph-c6fr"],"modified":"2026-08-15T11:30:56.158469018Z","published":"2026-08-12T21:11:55.180Z","database_specific":{"cna_assigner":"GitHub_M","cwe_ids":["CWE-444"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/73xxx/CVE-2026-73495.json"},"references":[{"type":"WEB","url":"https://github.com/http4s/blaze/releases/tag/v0.23.18"},{"type":"WEB","url":"https://github.com/http4s/blaze/releases/tag/v1.0.0-M42"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/73xxx/CVE-2026-73495.json"},{"type":"ADVISORY","url":"https://github.com/http4s/blaze/security/advisories/GHSA-46q4-43ph-c6fr"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-73495"},{"type":"FIX","url":"https://github.com/http4s/blaze/commit/ef3e666c146cfc16cb6603f1fc3c464daab4a24f"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/http4s/blaze","events":[{"introduced":"0"},{"fixed":"2ae13a74d55209b6573d5228d1aa94f0361a75d0"},{"fixed":"b2cb8e8591391409bb1df242b45433891251b1b1"},{"fixed":"ef3e666c146cfc16cb6603f1fc3c464daab4a24f"}],"database_specific":{"extracted_events":[{"introduced":"0"},{"fixed":"0.23.18"},{"introduced":"1.0.0-M1"},{"fixed":"1.0.0-M42"}],"source":["AFFECTED_FIELD","REFERENCES"]}}],"versions":["v1.0.0-M41","v0.23.17","v1.0.0-M40","v0.23.16","v1.0.0-M39","v0.23.15","v0.23.14","v1.0.0-M38","v1.0.0-M37","v0.23.13","v1.0.0-M36","v1.0.0-M35","v1.0.0-M34","v1.0.0-M33","v0.23.12","v0.15.3","v0.15.2","v0.15.1","v0.15.0","v0.15.0-M4","v0.15.0-M3","v0.15.0-M2","v0.15.0-M1","v0.14.14","v0.14.13","v0.14.12","v0.14.10","v0.14.8","v0.14.7","v0.14.6","v0.14.5","v0.14.4","v0.14.2","v0.14.0","v0.14.0-M12","v0.14.0-M11","v0.14.0-M10","v0.14.0-M9","v0.14.0-M7","v0.14.0-M3","v0.14.0-M2","v0.13.0","v0.12.0","v0.11.0","v0.10.0","v0.9.0","v0.8.1","v0.8.0","v0.7.0","v0.6.0","v0.5.0","v0.4.0","v0.3.0","v0.2.0","v0.1.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-73495.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N"}]}