CVE-2026-69204

CVE-2026-69204 is a critical-severity security vulnerability in org.http4s:http4s-ember-core_2.12 (maven), affecting versions <= 0.23.34. It is fixed in 0.23.35, 1.0.0-M47.

Does this CVE actually affect you?

Kodem shows which CVEs are reachable and running in your applications, so you fix what's exploitable, not just what's listed.

Thank you! Your submission has been received!
Oops! Something went wrong while submitting the form.

Runtime intelligence, not another scanner.

Summary

Http4s Ember accepts Transfer-Encoding combined with Content-Length (CL.TE request smuggling)

Ember's HTTP/1.1 request parser does not reject a message that carries both a
Transfer-Encoding and a Content-Length header. RFC 9112 §6.1 requires a
server to treat such a message as a framing error and close the connection.
An intermediary that follows the RFC's CL-strip-and-forward path (or that
prioritises Content-Length) will frame the body differently from Ember,
enabling HTTP request smuggling (CL.TE).

Server

Request smuggling when ember-server is an origin behind an intermediary that
forwards both headers over a keep-alive backend connection and frames by
Content-Length while Ember frames by chunked:

  • Front-end security bypass: the smuggled request reaches paths the
    intermediary's ACL/auth layer would have blocked, with attacker-chosen
    method and headers.
  • Cross-user request hijack: a dangling smuggled prefix concatenates with the
    next victim's request on the shared backend socket, capturing its headers.
  • Cache poisoning: the smuggled response is associated with the next request
    key in a caching proxy.

Client

ember-client shares the same parser on the response path. An upstream that
sends both headers can desync a pooled client connection. This requires a
malicious or compromised upstream.

Preconditions

  • Unauthenticated remote attacker (server)
  • ember-server as origin behind a keep-alive intermediary
  • Intermediary forwards a request carrying both Transfer-Encoding and
    Content-Length (RFC says it MAY reject; many forward) and frames by
    Content-Length
  • Malicious or compromised upstream (client)

Workarounds

  • Intermediary strictly rejects requests carrying both Transfer-Encoding
    and Content-Length
  • Intermediary buffers and re-encodes request bodies
  • Disable backend keep-alive between the intermediary and Ember

Impact

Affected versions

org.http4s:http4s-ember-core_2.12 (<= 0.23.34) org.http4s:http4s-ember-core_2.13 (<= 0.23.34) org.http4s:http4s-ember-core_3 (<= 0.23.34) org.http4s:http4s-ember-core_2.13 (>= 1.0.0-M1, <= 1.0.0-M46) org.http4s:http4s-ember-core_3 (>= 1.0.0-M1, <= 1.0.0-M46)

Security releases

org.http4s:http4s-ember-core_2.12 → 0.23.35 (maven) org.http4s:http4s-ember-core_2.13 → 0.23.35 (maven) org.http4s:http4s-ember-core_3 → 0.23.35 (maven) org.http4s:http4s-ember-core_2.13 → 1.0.0-M47 (maven) org.http4s:http4s-ember-core_3 → 1.0.0-M47 (maven)

Kodem intelligence

Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.

Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.

Already deployed Kodem?

See it in your environmentNew to Kodem? Get a demo →

Remediation advice

Upgrade the following packages to resolve this vulnerability:

org.http4s:http4s-ember-core_2.12 to 0.23.35 or later; org.http4s:http4s-ember-core_2.13 to 0.23.35 or later; org.http4s:http4s-ember-core_3 to 0.23.35 or later; org.http4s:http4s-ember-core_2.13 to 1.0.0-M47 or later; org.http4s:http4s-ember-core_3 to 1.0.0-M47 or later

Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.

Frequently Asked Questions

  1. What is CVE-2026-69204? CVE-2026-69204 is a critical-severity security vulnerability in org.http4s:http4s-ember-core_2.12 (maven), affecting versions <= 0.23.34. It is fixed in 0.23.35, 1.0.0-M47.
  2. Which packages are affected by CVE-2026-69204?
    • org.http4s:http4s-ember-core_2.12 (maven) (versions <= 0.23.34)
    • org.http4s:http4s-ember-core_2.13 (maven) (versions <= 0.23.34)
    • org.http4s:http4s-ember-core_3 (maven) (versions <= 0.23.34)
  3. Is there a fix for CVE-2026-69204? Yes. CVE-2026-69204 is fixed in 0.23.35, 1.0.0-M47. Upgrade to this version or later.
  4. Is CVE-2026-69204 exploitable, and should I be worried? Whether CVE-2026-69204 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
  5. What actually determines whether CVE-2026-69204 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
  6. How do I fix CVE-2026-69204?
    • Upgrade org.http4s:http4s-ember-core_2.12 to 0.23.35 or later
    • Upgrade org.http4s:http4s-ember-core_2.13 to 0.23.35 or later
    • Upgrade org.http4s:http4s-ember-core_3 to 0.23.35 or later
    • Upgrade org.http4s:http4s-ember-core_2.13 to 1.0.0-M47 or later
    • Upgrade org.http4s:http4s-ember-core_3 to 1.0.0-M47 or later

Stop the waste.
Protect your environment with Kodem.

Get a personalized demo
Get a personalized demo