CVE-2026-69204 Details
Description
Http4s 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.
A request smuggling vulnerability has been identified in Http4s versions prior to 0.23.35 and 1.0.0-M47. The issue arises in the Ember HTTP/1.1 request parser, which fails to reject messages containing both Transfer-Encoding and Content-Length headers. This oversight allows an intermediary to frame the message body differently than Ember, creating a request smuggling scenario. 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, bypassing access controls, poisoning caches, or hijacking requests. Additionally, this vulnerability can desynchronize an ember-client connection if a malicious upstream sends both headers.
Users can upgrade to Http4s versions 0.23.35 or 1.0.0-M47, both of which include the necessary fix. Instructions for downloading these versions are available on the Http4s GitHub Releases page.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed Sep 15, 2026CISA-ADP
Assessed Sep 15, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/http4s/http4s/commit/9feaf8677951a52af906ae9664ff6f0543d9d810 | [email protected] | Source CodeVendor |
| https://github.com/http4s/http4s/releases/tag/v0.23.35 | [email protected] | Release NotesVendor |
| https://github.com/http4s/http4s/releases/tag/v1.0.0-M47 | [email protected] | Release NotesVendor |
| https://github.com/http4s/http4s/security/advisories/GHSA-8h4c-x2wg-6xp8 | [email protected] | AdvisoryRemedyVendor |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-444 | Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| http4s | <= 0.23.34 (semver) ~1.0.0-M1, <= 1.0.0-M46 (semver) |
CPE
Remediation
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| http4s Ember | <= 0.23.34 (semver) ~1.0.0-M1, <= 1.0.0-M46 (semver) |
CPE
Remediation
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| http4s Ember Server | <= 0.23.34 (semver) ~1.0.0-M1, <= 1.0.0-M46 (semver) |
CPE
Remediation
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| http4s Ember Client | <= 0.23.34 (semver) ~1.0.0-M1, <= 1.0.0-M46 (semver) |
CPE
Remediation
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Change History
2 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Sep 15, 2026 | New CVE Received | [email protected] |
| Sep 15, 2026 | CVE Modified | CISA-ADP |