CVE-2026-69204
Fix: http4s/http4s@9feaf86CVE-2026-69204 is a CWE-444 vulnerability in org.http4s:http4s-ember-core_2.12. O3 Security confirms whether CVE-2026-69204 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Http4s: Ember accepts Transfer-Encoding combined with Content-Length (CL.TE request smuggling)
Exploitation Status
No confirmed exploitation observed yet
- A successful exploit gives an attacker total control of the affected component, not partial access.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-69204.
Real-World Exposure
org.http4s:http4s-ember-core_2.12☕org.http4s:http4s-ember-core_2.13☕org.http4s:http4s-ember-core_3☕org.http4s:http4s-ember-core_2.13☕org.http4s:http4s-ember-core_3Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.http4s:http4s-ember-core_2.12 | all versions | 0.23.35 |
| ☕Maven | org.http4s:http4s-ember-core_2.13 | all versions | 0.23.35 |
| ☕Maven | org.http4s:http4s-ember-core_3 | all versions | 0.23.35 |
| ☕Maven | org.http4s:http4s-ember-core_2.13 | ≥ 1.0.0-M1&&< 1.0.0-M47 | 1.0.0-M47 |
| ☕Maven | org.http4s:http4s-ember-core_3 | ≥ 1.0.0-M1&&< 1.0.0-M47 | 1.0.0-M47 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.http4s:http4s-ember-core_2.12. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update org.http4s:http4s-ember-core_2.12 to 0.23.35 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-69204 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-69204 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-69204. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-69204 in your dependencies?
O3 detects CVE-2026-69204 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.