GHSA-46Q4-43PH-C6FR
Vulnerability from github – Published: 2026-07-24 22:26 – Updated: 2026-08-12 21:12Summary
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 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.
{
"affected": [
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 0.23.17"
},
"package": {
"ecosystem": "Maven",
"name": "org.http4s:blaze-http_2.13"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.23.18"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 0.23.17"
},
"package": {
"ecosystem": "Maven",
"name": "org.http4s:blaze-http_2.12"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.23.18"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 0.23.17"
},
"package": {
"ecosystem": "Maven",
"name": "org.http4s:blaze-http_3"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.23.18"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "Maven",
"name": "org.http4s:blaze-http_3"
},
"ranges": [
{
"events": [
{
"introduced": "1.0.0-M1"
},
{
"fixed": "1.0.0-M42"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 1.0.0-M41"
},
"package": {
"ecosystem": "Maven",
"name": "org.http4s:blaze-http_2.13"
},
"ranges": [
{
"events": [
{
"introduced": "1.0.0-M1"
},
{
"fixed": "1.0.0-M42"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-73495"
],
"database_specific": {
"cwe_ids": [
"CWE-444"
],
"github_reviewed": true,
"github_reviewed_at": "2026-07-24T22:26:48Z",
"nvd_published_at": null,
"severity": "HIGH"
},
"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.",
"id": "GHSA-46q4-43ph-c6fr",
"modified": "2026-08-12T21:12:00Z",
"published": "2026-07-24T22:26:48Z",
"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"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N",
"type": "CVSS_V3"
}
],
"summary": "blaze: Chunked-body trailer fields promoted into Request.headers in blaze-server (front-end header-sanitization bypass)"
}
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