EUVD-2026-79193Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A06:2025 - Insecure Design
ASVS 5.0
V4 - API and Web Service HTTP request consistency
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Alert meAnalysisAIv1 – Sep 15, 2026
HTTP request smuggling in http4s Ember (all releases prior to 0.23.35 and 1.0.0-M47) lets an unauthenticated remote attacker bypass front-end proxy controls by sending duplicate Content-Length headers with differing values, because the Ember HTTP/1.1 parser accepts the conflict and frames the message using the last value instead of rejecting it as a framing error. When Ember runs behind a keep-alive intermediary that selects a different occurrence, the attacker can prepend a smuggled request to a later user's connection, capture that user's headers, or poison a shared cache; the same shared parser can also misframe upstream responses when an http4s client proxies for multiple downstream consumers. No public exploit code or CISA KEV entry was identified at time of analysis, but the CVSS 8.7 scope-changed rating makes this a priority fix for exposed Scala services sitting behind reverse proxies, CDNs, or load balancers.
Affected VersionsENISA
Affected Packages
Source: OSV (Open Source Vulnerabilities)
Affects your stack
Affects 2 packages in euvd
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Severity by source
AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N
Primary rating from Vendor (GitHub_M) · only source for this CVE.
CVSS VectorVendor: GitHub_M
Lifecycle Timeline
2DescriptionCVE.org
Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember’s HTTP/1.1 parser accepts differing duplicate Content-Length headers and uses the last value instead of rejecting the message. When an Ember server is behind a keep-alive intermediary that selects a different occurrence, an unauthenticated attacker can create CL.CL request smuggling that bypasses front-end controls, captures a later user’s headers, or poisons a cache. The shared client parser can also misframe responses from a malicious or compromised upstream when the client acts as a proxy for multiple downstream consumers. This issue is fixed in versions 0.23.35 and 1.0.0-M47.
Technical POC Analysis
Evidence note: the only artifact supplied is advisory GHSA-p83c-4wj9-p6w9.
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Threat Intelligence Overview
NVD
CVE.org
EPSS
GitHub
How this decision was reached
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What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.
HTTP request smuggling exploits inconsistencies in how front-end and back-end servers parse HTTP message boundaries.
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