What is the CVSS score of CVE-2026-73494?

CVE-2026-73494 has a CVSS 3.1 base score of 7.4 (High). CVSS vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N. EPSS exploitation probability: 0.4%.

Is there a patch available for CVE-2026-73494?

Yes, a patch is available for CVE-2026-73494. Update the affected software to the latest version immediately.

Blaze CVE-2026-73494

EUVD-2026-77697 HIGH

HTTP Request/Response Smuggling (CWE-444)

2026-09-14 GitHub_M

GHSA-mhvj-jhpq-885v

Authentication Bypass Java Request Smuggling Http4S Blaze Blaze Http 2 13 Blaze Http 3 Http4S Blaze Server 2 13

7.4

CVSS 3.1 · Vendor: GitHub_M

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Vulnerability Assessment

Weakness

CWE

CWE-444

OWASP Top 10:2025

A06:2025 - Insecure Design

ASVS 5.0

V4 - API and Web Service HTTP request consistency

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).

Patch available 0.4% exploitation probability (EPSS)

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AnalysisAIv1 – Sep 15, 2026

HTTP/1.1 request smuggling in http4s blaze allows a remote client to desynchronize message boundaries between blaze's hand-written Java wire parser and a fronting proxy, enabling front-end authorization bypass, response-queue poisoning on pooled backend connections, or cache poisoning. All deployments of blaze prior to 0.23.18, and the 1.0.0 milestone line from 1.0.0-M1 through 1.0.0-M41, are affected via five independent parser laxities that are reachable from a default BlazeServerBuilder with no non-default configuration. Exploitation is not confirmed in the wild and no public exploit code was identified at time of analysis; CISA SSVC records exploitation as none and automatable as no, and no EPSS score was supplied with the source data.

Affected VersionsENISA

http4s-blaze-server_2.13 < 0.23.18

blaze-http_3 1.0.0-M1, < 1.0.0-M42

blaze-http_2.13 1.0.0-M1, < 1.0.0-M42

blaze 1.0.0-M1, < 1.0.0-M42

blaze-http_3 < 0.23.18

blaze < 0.23.18

blaze-http_2.13 < 0.23.18

Affected Packages

maven org.http4s:blaze-http_2.13 fix: 0.23.18, 1.0.0-M42

maven org.http4s:blaze-http_3 fix: 0.23.18, 1.0.0-M42

maven org.http4s:http4s-blaze-server_2.13 fix: 0.23.18

euvd blaze fix: 0.23.18

euvd blaze_1_0_0_m1 fix: 1.0.0-M42

euvd blaze_http_2_13 fix: 0.23.18

euvd blaze_http_2_13_1_0_0_m1 fix: 1.0.0-M42

euvd blaze_http_3 fix: 0.23.18

euvd blaze_http_3_1_0_0_m1 fix: 1.0.0-M42

euvd http4s_blaze_server_2_13 fix: 0.23.18

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 10 packages in maven, euvd

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (GitHub_M) PRIMARY 7.4 HIGH

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

Primary rating from Vendor (GitHub_M) · only source for this CVE.

CVSS VectorVendor: GitHub_M

Attack Vector

Network

Attack Complexity

High

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

None

DescriptionCVE.org

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.

Blast Radius

ecosystem impact

† from your stack dependencies † transitive graph · vuln.today resolves 4-path depth

10 maven packages depend on org.http4s:http4s-blaze-server_2.13 (4 direct, 6 indirect)

Ecosystem-wide dependent count for version 0.23.18.

Technical POC Analysis

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

Full technical POC analysis - root cause, step-by-step exploitation and patch breakdown - is part of the Pro and Business plans.

Threat Intelligence Overview

EPSS Score

0.4%

Top 69% exploitable

Data Quality

6 sources

Confidence: High

EUVD

NVD

CVE.org

EPSS

Vulnrichment

GitHub

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity HIGH

CISA KEV No

Public POC No

EPSS 0.4%

Patch available Yes

Active threat No

Deciding rule

HIGH severity (CVSS 7.0-8.9)

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.