23 Oct 2026 15:48:27 UTC
Http4s: Ember accepts Transfer-Encoding combined with Content-Length (CL.TE request smuggling)
cve-program · CVE-2026-69204 · Published
CVE-2026-69204
Http4s: Ember accepts Transfer-Encoding combined with Content-Length (CL.TE request smuggling)
CVSS 4.0 9.2 CRITICALCheck source for fixed versionsKEV status unknown
cve-program · CVE-2026-69204
PublishedHttp4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember HTTP/1.1 does not reject messages containing both Transfer-Encoding and Content-Length, so an intermediary and Ember can select different body framing rules. When ember-server is behind a keep-alive intermediary that forwards both headers and frames by Content-Length, an unauthenticated attacker can smuggle a second request, bypass intermediary access controls, poison caches, or cause a victim request to be joined to an attacker-controlled prefix. The shared response parser can also desynchronize an ember-client connection when a malicious or compromised upstream sends both headers. This issue is fixed in versions 0.23.35 and 1.0.0-M47.
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