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TI-2026-51606 Aliases CVE-2026-73494GHSA-mhvj-jhpq-885v

blaze: Multiple HTTP/1.1 request-smuggling primitives in blaze's Java wire parser

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 from 1.0.0-M1 until 1.0.0-M42, five HTTP/1.1 conformance laxities in the hand-written Java parser under http/src/main/java/org/http4s/blaze/http/parser/ can cause blaze to derive a different request boundary than a stricter fronting intermediary. A default BlazeServerBuilder accepts invalid or valueless header field names that violate tchar syntax, obsolete folded field lines (obs-fold), unsupported Transfer-Encoding values, duplicate Content-Length fields, and requests containing both Transfer-Encoding and Content-Length. If a lenient or legacy proxy forwards the malformed bytes but interprets them differently, the disagreement can permit front-end authorization bypass, response-queue poisoning on pooled backend connections, or cache poisoning. Exploitation requires a pair of disagreeing parsers; no non-default blaze configuration is required. The affected checks are enforced in BodyAndHeaderParser and Http1ServerParser. 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 0.00628 50th percentileScored 2026-11-07
Fix Fixed blaze (http4s): 0.23.18, 1.0.0-M42blaze-http_2.13 (org.http4s): 0.23.18, 1.0.0-M42+5 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.http4sblaze-http_2.13before 0.23.18; 1.0.0-M1 to before 1.0.0-M420.23.18, 1.0.0-M42Patch availableCNA
org.http4sblaze-http_3before 0.23.18; 1.0.0-M1 to before 1.0.0-M420.23.18, 1.0.0-M42Patch availableCNA
org.http4shttp4s-blaze-server_2.13before 0.23.180.23.18Patch availableCNA
—org.http4s:http4s-blaze-server_2.13 (Maven)before 0.23.180.23.18Patch availableGHSA-mhvj-jhpq-885v
—org.http4s:blaze-http_2.13 (Maven)before 0.23.180.23.18Patch availableGHSA-mhvj-jhpq-885v
—org.http4s:blaze-http_3 (Maven)before 0.23.180.23.18Patch availableGHSA-mhvj-jhpq-885v
—org.http4s:blaze-http_3 (Maven)1.0.0-M1 to before 1.0.0-M421.0.0-M42Patch availableGHSA-mhvj-jhpq-885v
—org.http4s:blaze-http_2.13 (Maven)1.0.0-M1 to before 1.0.0-M421.0.0-M42Patch availableGHSA-mhvj-jhpq-885v
  • 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
  • blaze-http_2.13 Vendororg.http4s 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
  • blaze-http_3 Vendororg.http4s 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
  • http4s-blaze-server_2.13 Vendororg.http4s Affected before 0.23.18 Fixed in 0.23.18 Patch available CNA
  • org.http4s:http4s-blaze-server_2.13 (Maven) Vendor— Affected before 0.23.18 Fixed in 0.23.18 Patch available GHSA-mhvj-jhpq-885v
  • org.http4s:blaze-http_2.13 (Maven) Vendor— Affected before 0.23.18 Fixed in 0.23.18 Patch available GHSA-mhvj-jhpq-885v
  • org.http4s:blaze-http_3 (Maven) Vendor— Affected before 0.23.18 Fixed in 0.23.18 Patch available GHSA-mhvj-jhpq-885v
  • 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-mhvj-jhpq-885v
  • 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-mhvj-jhpq-885v

Remediation

  • Fix · CNA blaze (http4s) Fixed in 0.23.18, 1.0.0-M42
  • Fix · CNA blaze-http_2.13 (org.http4s) Fixed in 0.23.18, 1.0.0-M42
  • Fix · CNA blaze-http_3 (org.http4s) Fixed in 0.23.18, 1.0.0-M42
  • Fix · CNA http4s-blaze-server_2.13 (org.http4s) Fixed in 0.23.18
  • Fix · GHSA-mhvj-jhpq-885v org.http4s:http4s-blaze-server_2.13 (Maven) Fixed in 0.23.18 Advisory →
  • Fix · GHSA-mhvj-jhpq-885v org.http4s:blaze-http_2.13 (Maven) Fixed in 0.23.18 Advisory →
  • Fix · GHSA-mhvj-jhpq-885v org.http4s:blaze-http_3 (Maven) Fixed in 0.23.18 Advisory →
  • Fix · GHSA-mhvj-jhpq-885v org.http4s:blaze-http_3 (Maven) Fixed in 1.0.0-M42 Advisory →
  • Fix · GHSA-mhvj-jhpq-885v org.http4s:blaze-http_2.13 (Maven) Fixed in 1.0.0-M42 Advisory →

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-73494
  2. 2026-10-03 Alias added: GHSA-mhvj-jhpq-885v
  3. 2026-10-30 EPSS moved to the 50th–90th percentile

References

Other 10

  • 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

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