Http4s: Ember Server accepts duplicate Content-Length headers

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-69217
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-15 20:17:41 UTC
Updated2026-09-16 20:39:16 UTC
DescriptionHttp4s 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.

Risk And Classification

Primary CVSS: v3.1 8.7 HIGH from [email protected]

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N

EPSS: 0.004990000 probability, percentile 0.415070000 (date 2026-09-16)

Problem Types: CWE-444 | CWE-444 CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary8.7HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N
3.1CNADECLARED8.7HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Http4s Http4s affected < 0.23.35 Not specified
CNA Http4s Http4s affected >= 1.0.0-M1, < 1.0.0-M47 Not specified

References

ReferenceSourceLinkTags
github.com/http4s/http4s/commit/24e8d34e3ea89f8f23e0053ec9944f6467e8086d [email protected] github.com
github.com/http4s/http4s/releases/tag/v1.0.0-M47 [email protected] github.com
github.com/http4s/http4s/releases/tag/v0.23.35 [email protected] github.com
github.com/http4s/http4s/security/advisories/GHSA-p83c-4wj9-p6w9 [email protected] github.com
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