Http4S
CVE-2025-59822
MEDIUM
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A06:2025 - Insecure Design
ASVS 5.0
V4 - API and Web Service HTTP request consistency
|
| Impact | CVSS score of 6.3 (MEDIUM). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required. Public proof-of-concept exploit code is available. EPSS exploitation probability: 0.07%. |
| Exploit ScenarioDerived | A remote attacker could manipulate HTTP request interpretation between frontend and backend servers by sending crafted requests to the affected application. No authentication is required to exploit this vulnerability. |
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Alert meAnalysisAIv1 – Mar 28, 2026
Http4s is a Scala interface for HTTP services. Rated medium severity (CVSS 6.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.
RemediationAI
A vendor patch is available. Apply the latest security update as soon as possible. Enforce strict HTTP parsing, normalize requests at proxy layer, use HTTP/2 end-to-end, reject ambiguous headers.
Affected Packages
Source: OSV (Open Source Vulnerabilities)
Affects your stack
Affects 3 packages in maven
Checking this CVE against your own stacks and servers is part of the Basic plan and up.
Technical ContextAI · show details
This vulnerability is classified as HTTP Request/Response Smuggling (CWE-444), which allows attackers to manipulate HTTP request interpretation between frontend and backend servers. Http4s is a Scala interface for HTTP services. In versions from 1.0.0-M1 to before 1.0.0-M45 and before 0.23.31, http4s is vulnerable to HTTP Request Smuggling due to improper handling of HTTP trailer section. This vulnerability could enable attackers to bypass front-end servers security controls, launch targeted attacks against active users, and poison web caches. A pre-requisite for exploitation involves the web application being deployed behind a reverse-proxy that forwards trailer headers. This issue has been patched in versions 1.0.0-M45 and 0.23.31. Affected products include: Typelevel Http4S. Version information: before 1.0.0.
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- Exploit and PoC references, threat intelligence from 22 sources
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Severity by source
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
Primary rating from Vendor (github) · only source for this CVE.
CVSS VectorVendor: github
Lifecycle Timeline
3DescriptionCVE.org
Http4s is a Scala interface for HTTP services. In versions from 1.0.0-M1 to before 1.0.0-M45 and before 0.23.31, http4s is vulnerable to HTTP Request Smuggling due to improper handling of HTTP trailer section. This vulnerability could enable attackers to bypass front-end servers security controls, launch targeted attacks against active users, and poison web caches. A pre-requisite for exploitation involves the web application being deployed behind a reverse-proxy that forwards trailer headers. This issue has been patched in versions 1.0.0-M45 and 0.23.31.
Executive ViewAI
Organizations using versions from 1.0.0-M1 to should be aware of moderate risk from CVE-2025-59822 rated CVSS 6.3. Exploitation could compromise the security of affected deployments. Proof-of-concept code is publicly available. A patch is available and should be applied during regular vulnerability management.
Apply vendor patch. If patching is delayed: restrict network access and enable monitoring.
Threat Intelligence Overview
NVD
CVE.org
EPSS
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.
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.
Affected Products (CPE)CVE.org
XML External Entity (XXE) injection in http4s-scala-xml's EntityDecoder for scala.xml.Elem (all versions before 0.24.1 a
Http4s client applications that keep a cookie jar can leak stored cookies — including session and authentication cookies
Http4s is a Scala interface for HTTP services. Rated medium severity (CVSS 5.3), this vulnerability is remotely exploita
Request smuggling in the http4s Ember HTTP/1.1 parser lets an unauthenticated, remote attacker bypass front-end access c
Http4s is a minimal, idiomatic Scala interface for HTTP services. Rated critical severity (CVSS 9.1), this vulnerability
HTTP request smuggling in http4s Ember (all releases prior to 0.23.35 and 1.0.0-M47) lets an unauthenticated remote atta
Let me synthesize. CVE-2026-69205: http4s Ember HTTP parser request smuggling via Transfer-Encoding header case-sensiti
http4s is an open source scala interface for HTTP. Rated medium severity (CVSS 4.7), this vulnerability is remotely expl
A crafted WebSocket frame can pin a worker thread and exhaust memory in the http4s Scala HTTP library, causing denial of
Heap exhaustion in the http4s Ember backend (0.23.x before 0.23.35 and 1.0.0 milestones before 1.0.0-M47) allows a singl
Heap-exhaustion denial of service in the http4s DigestAuth server middleware: an inverted stale-nonce comparison in Nonc
Unbounded WebSocket fragment aggregation in http4s-blaze-server allows any client that completes a WebSocket handshake t
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