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TI-2026-51607 Aliases CVE-2026-73495GHSA-46q4-43ph-c6fr

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

Priority LOW 35CWE-444Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
High
Impact type
—
Confidentiality · integrity · availability
High · High · None
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub.

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.0048 41st percentileScored 2026-11-07
Fix Fixed blaze (http4s): 0.23.18, 1.0.0-M42org.http4s:blaze-http_2.13 (Maven): 0.23.18, 1.0.0-M42+2 more products

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
http4sblazebefore 0.23.18; 1.0.0-M1 to before 1.0.0-M420.23.18, 1.0.0-M42Patch availableCNA
—org.http4s:blaze-http_2.13 (Maven)before 0.23.180.23.18Patch availableGHSA-46q4-43ph-c6fr
—org.http4s:blaze-http_2.12 (Maven)before 0.23.180.23.18Patch availableGHSA-46q4-43ph-c6fr
—org.http4s:blaze-http_3 (Maven)before 0.23.180.23.18Patch availableGHSA-46q4-43ph-c6fr
—org.http4s:blaze-http_3 (Maven)1.0.0-M1 to before 1.0.0-M421.0.0-M42Patch availableGHSA-46q4-43ph-c6fr
—org.http4s:blaze-http_2.13 (Maven)1.0.0-M1 to before 1.0.0-M421.0.0-M42Patch availableGHSA-46q4-43ph-c6fr
  • blaze Vendorhttp4s Affected before 0.23.18; 1.0.0-M1 to before 1.0.0-M42 Fixed in 0.23.18, 1.0.0-M42 Patch available CNA
  • org.http4s:blaze-http_2.13 (Maven) Vendor— Affected before 0.23.18 Fixed in 0.23.18 Patch available GHSA-46q4-43ph-c6fr
  • org.http4s:blaze-http_2.12 (Maven) Vendor— Affected before 0.23.18 Fixed in 0.23.18 Patch available GHSA-46q4-43ph-c6fr
  • org.http4s:blaze-http_3 (Maven) Vendor— Affected before 0.23.18 Fixed in 0.23.18 Patch available GHSA-46q4-43ph-c6fr
  • org.http4s:blaze-http_3 (Maven) Vendor— Affected 1.0.0-M1 to before 1.0.0-M42 Fixed in 1.0.0-M42 Patch available GHSA-46q4-43ph-c6fr
  • org.http4s:blaze-http_2.13 (Maven) Vendor— Affected 1.0.0-M1 to before 1.0.0-M42 Fixed in 1.0.0-M42 Patch available GHSA-46q4-43ph-c6fr

Remediation

  • Fix · CNA blaze (http4s) Fixed in 0.23.18, 1.0.0-M42
  • Fix · GHSA-46q4-43ph-c6fr org.http4s:blaze-http_2.13 (Maven) Fixed in 0.23.18 Advisory →
  • Fix · GHSA-46q4-43ph-c6fr org.http4s:blaze-http_2.12 (Maven) Fixed in 0.23.18 Advisory →
  • Fix · GHSA-46q4-43ph-c6fr org.http4s:blaze-http_3 (Maven) Fixed in 0.23.18 Advisory →
  • Fix · GHSA-46q4-43ph-c6fr org.http4s:blaze-http_3 (Maven) Fixed in 1.0.0-M42 Advisory →
  • Fix · GHSA-46q4-43ph-c6fr org.http4s:blaze-http_2.13 (Maven) Fixed in 1.0.0-M42 Advisory →

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-73495
  2. 2026-10-03 Alias added: GHSA-46q4-43ph-c6fr

References

Other 5

  • TI-2022-13223 mTLS client verification is skipped in fs2 on Node.js CVSS 3.1CRITICAL 9.8
  • TI-2023-08714 Http4s has fatal error parsing User-Agent and Server headers CVSS 3.1HIGH 7.5
  • TI-2022-06031 Hash collision in typelevel jawn CVSS 3.1HIGH 7.5
  • TI-2025-37261 Http4s vulnerable to HTTP Request Smuggling due to improper handling of HTTP trailer section CVSS 4.0MEDIUM 6.3
  • TI-2026-44185 http4s-scala-xml has an XML External Entity (XXE) processing issue CVSS 3.1CRITICAL 9.3
  • TI-2020-04336 Local file inclusion vulnerability in http4s CVSS 3.1HIGH 7.6
See all 36 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences