{"id":"CVE-2026-73495","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-73495","summary":"blaze: Chunked-body trailer fields promoted into Request.headers in blaze-server (front-end header-sanitization bypass)","details":"### Summary\n  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/values (e.g. `X-Forwarded-For`, internal-auth headers) that a fronting proxy sanitized from the request-header section, bypassing header-based trust decisions in the application.\n\n  ### Impact\n  Any http4s application using `BlazeServerBuilder` over HTTP/1.1 whose routes or middleware trust proxy-set headers (e.g., `X-Forwarded-For`, `X-Real-IP`, `X-Forwarded-Host`, org-internal auth headers) is affected. Where a fronting proxy strips/normalizes those headers but forwards chunked bodies with trailers intact, an attacker can spoof client IP for allow-lists/rate-limits/audit, forge the `https` scheme, or inject internal-auth headers. A promoted `Connection: close` trailer is also honored, allowing attacker-controlled termination of pooled backend connections.\n\n  ### Workarounds\n  Deploy behind a proxy that removes trailer fields (or rejects requests that use trailers) before forwarding; until patched, avoid trust decisions based on headers that a proxy is relied upon to sanitize.","published":"2026-07-24T22:26:48Z","modified":"2026-08-12T21:15:09.043811083Z","cvss":{"score":7.4,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"Maven","name":"org.http4s:blaze-http_2.13","fixedVersion":"0.23.18"},{"ecosystem":"Maven","name":"org.http4s:blaze-http_2.12","fixedVersion":"0.23.18"},{"ecosystem":"Maven","name":"org.http4s:blaze-http_3","fixedVersion":"0.23.18"},{"ecosystem":"Maven","name":"org.http4s:blaze-http_3","fixedVersion":"1.0.0-M42"},{"ecosystem":"Maven","name":"org.http4s:blaze-http_2.13","fixedVersion":"1.0.0-M42"}],"fix":{"url":"https://github.com/http4s/blaze/commit/ef3e666c146cfc16cb6603f1fc3c464daab4a24f","label":"http4s/blaze@ef3e666"},"references":[{"type":"WEB","url":"https://github.com/http4s/blaze/security/advisories/GHSA-46q4-43ph-c6fr"},{"type":"WEB","url":"https://github.com/http4s/blaze/commit/ef3e666c146cfc16cb6603f1fc3c464daab4a24f"},{"type":"PACKAGE","url":"https://github.com/http4s/blaze"},{"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"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T21:15:09.043811083Z"}}