High, CVSS 7.4MavenPublished
blaze: Chunked-body trailer fields promoted into Request.headers in blaze-server (front-end header-sanitization bypass)
CVE-2026-73495 · GHSA-46q4-43ph-c6fr
- Affected
- Maven org.http4s:blaze-http_2.12 <= 0.23.17
- Fixed in
- 0.23.18· Vendor fix available
- Issue
- 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. Impact 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. Workarounds Deploy behind a proxy that…
Recommended action: Upgrade to 0.23.18 or later, then redeploy and verify.A vendor fix does not resolve your finding until you verify it in your own systems.