GHSA-8h4c-x2wg-6xp8
Fix: http4s/http4s@9feaf86GHSA-8h4c-x2wg-6xp8 is a CWE-444 vulnerability in org.http4s:http4s-ember-core_2.12. O3 Security confirms whether GHSA-8h4c-x2wg-6xp8 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 GHSA-8h4c-x2wg-6xp8.
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
Summary
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).
Impact
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-EncodingandContent-Length(RFC says it MAY reject; many forward) and frames byContent-Length - Malicious or compromised upstream (client)
Workarounds
- Intermediary strictly rejects requests carrying both
Transfer-EncodingandContent-Length - Intermediary buffers and re-encodes request bodies
- Disable backend keep-alive between the intermediary and Ember
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 GHSA-8h4c-x2wg-6xp8 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 GHSA-8h4c-x2wg-6xp8 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 GHSA-8h4c-x2wg-6xp8. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-8h4c-x2wg-6xp8 in your dependencies?
O3 detects GHSA-8h4c-x2wg-6xp8 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.