Http4s: Ember Transfer-Encoding value parsing (TE.CL / TE.0 request smuggling)

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-69205
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-15 20:17:39 UTC
Updated2026-09-15 20:17:39 UTC
DescriptionHttp4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember’s HeaderP.parse uses a case-sensitive substring test for the Transfer-Encoding value and decodes header bytes with the platform default charset. Values such as Chunked are not recognized, values such as notchunked are incorrectly accepted, and Unicode case folding can turn a Kelvin-sign byte sequence into a match when UTF-8 is used. Intermediaries that apply RFC-compliant token and charset rules can therefore disagree with Ember’s Content-Length or zero-length framing, enabling TE.CL or TE.0 request smuggling, access-control bypass, cross-user request hijacking, and cache poisoning on the server path. Response smuggling through an ember-client gateway requires a malicious or compromised upstream. 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

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/5e88b2e7b4e6ea2f0c61040a4bc9de0d73e51217 [email protected] github.com
github.com/http4s/http4s/releases/tag/v1.0.0-M47 [email protected] github.com
github.com/http4s/http4s/security/advisories/GHSA-9998-894r-fwvr [email protected] github.com
github.com/http4s/http4s/releases/tag/v0.23.35 [email protected] github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

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