Vulnerabilities in pkg:maven/org.http4s/blaze-http_2.13

PACKAGE
Advisory Identifier: GHSA-mhvj-jhpq-885v
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Advisory Summary

CVE-2026-73494 is a HIGH (CVSS 7.4) multiple http/1.1 request-smuggling primitives vulnerability (CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')) affecting blaze libraries in the Maven ecosystem. The issue involves multiple http/1.1 request-smuggling primitives in blaze's java wire parser. Remediation is available by upgrading affected packages to version 0.23.18, 1.0.0-M42.

2 Known Advisory Record(s)
Package Vulnerability Intelligence

pkg:maven/org.http4s/blaze-http_2.13

2 Known Advisory Record(s)

Vulnerability advisories affecting package pkg:maven/org.http4s/blaze-http_2.13. Select an advisory below to view technical details or fixes.

Advisory ID CVE / NVD Severity Summary
GHSA-mhvj-jhpq-885v CVE-2026-73494 HIGH blaze: Multiple HTTP/1.1 request-smuggling primitives in blaze's Java wire parser
GHSA-46q4-43ph-c6fr CVE-2026-73495 HIGH blaze: Chunked-body trailer fields promoted into Request.headers in blaze-server (front-end header-sanitization bypass)

CVE-2026-73494 at a Glance

CVE Identifier CVE-2026-73494
GHSA Identifier GHSA-mhvj-jhpq-885v
Severity HIGH
CVSS v3.1 Base Score 7.4
CWE Classification CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Affected Product blaze
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 7.4

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N).

Attack Vector Network (AV:N)
Attack Complexity High (AC:H)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity High (I:H)
Availability None (A:N)

How to Fix CVE-2026-73494

To remediate this vulnerability, upgrade all affected blaze dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

org.http4s:http4s-blaze-server_2.13 fixed: 0.23.18 
<dependency>
    <groupId>org.http4s</groupId>
    <artifactId>http4s-blaze-server_2.13</artifactId>
    <version>0.23.18</version>
</dependency>
org.http4s:blaze-http_2.13 fixed: 0.23.18 
<dependency>
    <groupId>org.http4s</groupId>
    <artifactId>blaze-http_2.13</artifactId>
    <version>0.23.18</version>
</dependency>
org.http4s:blaze-http_3 fixed: 0.23.18 
<dependency>
    <groupId>org.http4s</groupId>
    <artifactId>blaze-http_3</artifactId>
    <version>0.23.18</version>
</dependency>
org.http4s:blaze-http_3 fixed: 1.0.0-M42 
<dependency>
    <groupId>org.http4s</groupId>
    <artifactId>blaze-http_3</artifactId>
    <version>1.0.0-M42</version>
</dependency>
org.http4s:blaze-http_2.13 fixed: 1.0.0-M42 
<dependency>
    <groupId>org.http4s</groupId>
    <artifactId>blaze-http_2.13</artifactId>
    <version>1.0.0-M42</version>
</dependency>
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

mvn dependency:tree -Dincludes=org.http4s

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2026-73494, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree -Dincludes=org.http4s

Analyze the terminal output to locate any version of blaze in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.23.18), your application is affected.

Note: The mvn dependency:tree -Dincludes=org.http4s command inspects the resolved dependency graph declared in your project's POM files; it does not perform automated security scanning or inspect runtime dynamic classpaths. Always verify runtime container classpaths and shaded JARs.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling'), where the product acts as an intermediary http agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed http requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination. In blaze, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Summary Five independent HTTP/1.1 conformance laxities in blaze's hand-written Java parser (`http/src/main/java/org/http4s/blaze/http/parser/`) cause request-boundary disagreement with a stricter intermediary. All are reachable from a default `BlazeServerBuilder` with no non-default configuration. ### Impact Actual exploitability depends on the fronting proxy — a boundary disagreement requires a *pair* of parsers that disagree. Where the proxy forwards the malformed bytes and derives a different message boundary, the consequences are the standard set: front-end ACL/auth bypass, response-queue poisoning on pooled backend connections, and cache poisoning. Risk concentrates on lenient or legacy intermediaries. ### Workarounds Deploy behind an RFC-strict reverse proxy (nginx, HAProxy, Envoy, ALB) that rejects or re-serializes malformed requests at the edge; this neutralizes most of these for deployments that cannot upgrade immediately.

CVE-2026-73494 Affected blaze Versions

5 component(s)
Fixed Versions:
0.23.181.0.0-M42
Product / Package Ecosystem Affected Versions Fixed Version
org.http4s:http4s-blaze-server_2.13
maven/org.http4s/http4s-blaze-server_2.13
Maven
< 0.23.18
0.23.18
org.http4s:blaze-http_2.13
maven/org.http4s/blaze-http_2.13
Maven
< 0.23.18
0.23.18
org.http4s:blaze-http_3
maven/org.http4s/blaze-http_3
Maven
< 0.23.18
0.23.18
org.http4s:blaze-http_3
maven/org.http4s/blaze-http_3
Maven
≥ 1.0.0-M1
< 1.0.0-M42
1.0.0-M42
org.http4s:blaze-http_2.13
maven/org.http4s/blaze-http_2.13
Maven
≥ 1.0.0-M1
< 1.0.0-M42
1.0.0-M42

References

GitHub Advisory / Wiki ADVISORY
https://github.com/http4s/blaze/security/advisories/GHSA-mhvj-jhpq-885v
Security Fix Commit FIX COMMIT
https://github.com/http4s/blaze/commit/3f7c022e306631b006dcb43a1d7f65c0d1966f17
Security Fix Commit FIX COMMIT
https://github.com/http4s/blaze/commit/4eec2007806aa9acfefb00ebb636ddc39a147a96
Security Fix Commit FIX COMMIT
https://github.com/http4s/blaze/commit/927b67753a78c13c4445dac9307f511f5c4878c3
Security Fix Commit FIX COMMIT
https://github.com/http4s/blaze/commit/a54bc9cd31758335c7f24e29763622fd03fcf734
Security Fix Commit FIX COMMIT
https://github.com/http4s/blaze/commit/c47d9675f87603f11b32a11d503626bdf9be5c7a
Security Fix Commit FIX COMMIT
https://github.com/http4s/blaze/commit/e871ebb1d27f50c98fd56988526ce42d0fee74d6
blaze Source Repository REPOSITORY
https://github.com/http4s/blaze
blaze Release RELEASE
https://github.com/http4s/blaze/releases/tag/v0.23.18
blaze Release RELEASE
https://github.com/http4s/blaze/releases/tag/v1.0.0-M42

Frequently Asked Questions

What is CVE-2026-73494?
CVE-2026-73494 is a security vulnerability in blaze involving Multiple HTTP/1.1 request-smuggling primitives in blaze's Java wire parser under CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling').
Which blaze versions are affected?
Affected versions include releases prior to 0.23.18, 1.0.0-M42 across affected packages: org.http4s:http4s-blaze-server_2.13, org.http4s:blaze-http_2.13, org.http4s:blaze-http_3.
What version fixes CVE-2026-73494?
Upgrading to 0.23.18, 1.0.0-M42 (or the latest patched release for your respective branch) resolves the vulnerability.
Is http4s-blaze-server_2.13 affected?
Yes, org.http4s:http4s-blaze-server_2.13 is affected in releases prior to 0.23.18. Upgrade your dependency to 0.23.18 or later.
Is blaze-http_2.13 affected?
Yes, org.http4s:blaze-http_2.13 is affected in releases prior to 0.23.18, 1.0.0-M42. Upgrade your dependency to 0.23.18, 1.0.0-M42 or later.
What is the CVSS score of CVE-2026-73494?
CVE-2026-73494 has a CVSS v3.1 base score of 7.4 (HIGH) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N.
What CWE is associated with CVE-2026-73494?
CVE-2026-73494 is classified under CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') (The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.).
How can I check Maven dependencies for CVE-2026-73494?
Run the dependency tree command: 'mvn dependency:tree -Dincludes=org.http4s'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-mhvj-jhpq-885v",
  "modified" : "2026-08-12T21:12:10Z",
  "published" : "2026-07-24T22:26:27Z",
  "aliases" : [ "CVE-2026-73494" ],
  "summary" : "blaze: Multiple HTTP/1.1 request-smuggling primitives in blaze's Java wire parser",
  "details" : "### Summary\n  Five independent HTTP/1.1 conformance laxities in blaze's hand-written Java parser (`http/src/main/java/org/http4s/blaze/http/parser/`) cause request-boundary disagreement with a stricter intermediary. All are reachable from a default `BlazeServerBuilder` with no non-default configuration.\n\n### Impact\nActual exploitability depends on the fronting proxy — a boundary disagreement requires a *pair* of parsers that disagree. Where the proxy forwards the malformed bytes and derives a different message boundary, the consequences are the standard set: front-end ACL/auth bypass, response-queue poisoning on pooled backend connections, and cache poisoning. Risk concentrates on lenient or legacy intermediaries.\n\n### Workarounds\n  Deploy behind an RFC-strict reverse proxy (nginx, HAProxy, Envoy, ALB) that rejects or re-serializes malformed requests at the edge; this neutralizes most of these for deployments that cannot upgrade immediately.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
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    },
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      }, {
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      } ]
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    "database_specific" : {
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    }
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    "database_specific" : {
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    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
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      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 1.0.0-M41"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/http4s/blaze/security/advisories/GHSA-mhvj-jhpq-885v"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/http4s/blaze/commit/3f7c022e306631b006dcb43a1d7f65c0d1966f17"
  }, {
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    "url" : "https://github.com/http4s/blaze/commit/4eec2007806aa9acfefb00ebb636ddc39a147a96"
  }, {
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    "url" : "https://github.com/http4s/blaze/commit/927b67753a78c13c4445dac9307f511f5c4878c3"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/http4s/blaze/commit/a54bc9cd31758335c7f24e29763622fd03fcf734"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/http4s/blaze/commit/c47d9675f87603f11b32a11d503626bdf9be5c7a"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/http4s/blaze/commit/e871ebb1d27f50c98fd56988526ce42d0fee74d6"
  }, {
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  }, {
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  }, {
    "type" : "WEB",
    "url" : "https://github.com/http4s/blaze/releases/tag/v1.0.0-M42"
  } ],
  "database_specific" : {
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    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-24T22:26:27Z",
    "nvd_published_at" : null
  }
}