Vulnerability-Lookup

CVE-2026-73495 (GCVE-0-2026-73495)

Vulnerability from cvelistv5 – Published: 2026-08-12 21:11 – Updated: 2026-08-13 13:04

Title

blaze: Chunked-body trailer fields promoted into Request.headers in blaze-server (front-end header-sanitization bypass)

Summary

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.

Severity

7.4 (High)


                        
                          CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

SSVC

Exploitation: none Automatable: no Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-13 13:02 UTC

CWE

CWE-444 - Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

Assigner

GitHub_M mitre root

References

4 references

URL	Tags
https://github.com/http4s/blaze/security/advisori…	x_refsource_CONFIRM
https://github.com/http4s/blaze/commit/ef3e666c14…	x_refsource_MISC
https://github.com/http4s/blaze/releases/tag/v0.23.18	x_refsource_MISC
https://github.com/http4s/blaze/releases/tag/v1.0.0-M42	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
http4s	blaze	Affected: < 0.23.18 Affected: >= 1.0.0-M1, < 1.0.0-M42	guessed

Show details on NVD website

JSON

To clipboard

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                "id": "CVE-2026-73495",
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FKIE_CVE-2026-73495

Vulnerability from fkie_nvd - Published: 2026-08-12 22:17 - Updated: 2026-08-13 13:19

Severity

7.4 (High) - CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/http4s/blaze/commit/ef3e666c146cfc16cb6603f1fc3c464daab4a24f
	security-advisories@github.com	https://github.com/http4s/blaze/releases/tag/v0.23.18
	security-advisories@github.com	https://github.com/http4s/blaze/releases/tag/v1.0.0-M42
	security-advisories@github.com	https://github.com/http4s/blaze/security/advisories/GHSA-46q4-43ph-c6fr

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "blaze",
          "vendor": "http4s",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 0.23.18"
            },
            {
              "status": "affected",
              "version": "\u003e= 1.0.0-M1, \u003c 1.0.0-M42"
            }
          ]
        }
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    }
  ],
  "id": "CVE-2026-73495",
  "lastModified": "2026-08-13T13:19:18.217",
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          "confidentialityImpact": "HIGH",
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GHSA-46Q4-43PH-C6FR

Vulnerability from github – Published: 2026-07-24 22:26 – Updated: 2026-08-12 21:12

Summary

blaze: Chunked-body trailer fields promoted into Request.headers in blaze-server (front-end header-sanitization bypass)

Details

Summary

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.

Severity

7.4 (High)


                  
                    CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

Show details on source website

JSON

To clipboard

{
  "affected": [
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      "database_specific": {
        "last_known_affected_version_range": "\u003c= 0.23.17"
      },
      "package": {
        "ecosystem": "Maven",
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    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 0.23.17"
      },
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          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 1.0.0-M41"
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        "ecosystem": "Maven",
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      },
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          "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)"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.

Action not permitted

CVE-2026-73495 (GCVE-0-2026-73495)

FKIE_CVE-2026-73495

GHSA-46Q4-43PH-C6FR

Summary

Tags

Sightings

Nomenclature