# CVE-2026-69216: Http4s Ember chunk parser lenience in HTTP request smuggling

Source: https://junglewise.ai/threats/cve-2026-69216-http4s-ember-chunk-parser-lenience-in-http-request-smuggling  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-15. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-69216 · Severity: medium · CVSS 5.4 · Published 2026-09-15

Http4s Ember is a Java/Scala HTTP client and server library. The chunk decoder is too lenient in parsing chunk sizes, accepting leading/trailing whitespace and +/- signs, which allows attackers to craft malformed chunked requests that intermediaries may interpret differently. When an Ember-based server sits behind a proxy, this can allow request smuggling to bypass security controls, poison caches, or hijack request queues.

Technologies: [Http4s-Ember-Core](https://junglewise.ai/threats/technologies/http4s-ember-core), [org.http4s:http4s-ember-core_2.12 (Maven)](https://junglewise.ai/threats/technologies/org-http4s-http4s-ember-core-2-12), [org.http4s:http4s-ember-core_2.13 (Maven)](https://junglewise.ai/threats/technologies/org-http4s-http4s-ember-core-2-13), [org.http4s:http4s-ember-core_3 (Maven)](https://junglewise.ai/threats/technologies/org-http4s-http4s-ember-core-3). Vendors: [Http4s](https://junglewise.ai/threats/vendors/http4s), [Maven](https://junglewise.ai/threats/vendors/maven).

## Quick answers

**Is CVE-2026-69216 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-69216 being exploited in the wild.

**How severe is CVE-2026-69216?** Medium severity, with a CVSS score of 5.4, published 15 September 2026.

**Which products and versions are affected?** Http4s-Ember-Core <= 0.23.34; org.http4s:http4s-ember-core_2.12 (Maven) ECOSYSTEM:introduced=0,fixed=0.23.35; org.http4s:http4s-ember-core_2.13 (Maven) ECOSYSTEM:introduced=0,fixed=0.23.35; org.http4s:http4s-ember-core_3 (Maven) ECOSYSTEM:introduced=0,fixed=0.23.35.

**Is there a fix for CVE-2026-69216?** Yes. org.http4s:http4s-ember-core_2.12 (Maven): upgrade to 0.23.35 or later; org.http4s:http4s-ember-core_2.13 (Maven): upgrade to 0.23.35 or later; org.http4s:http4s-ember-core_3 (Maven): upgrade to 0.23.35 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-69216 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-69216?** Check whether you run Http4s-Ember-Core, org.http4s:http4s-ember-core_2.12 (Maven), org.http4s:http4s-ember-core_2.13 (Maven) or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- org.http4s:http4s-ember-core_2.12 (Maven): upgrade to 0.23.35 or later

  ```sh
  # set org.http4s:http4s-ember-core_2.12 to 0.23.35 in your pom.xml or build.gradle
  ```

- org.http4s:http4s-ember-core_2.13 (Maven): upgrade to 0.23.35 or later

  ```sh
  # set org.http4s:http4s-ember-core_2.13 to 0.23.35 in your pom.xml or build.gradle
  ```

- org.http4s:http4s-ember-core_3 (Maven): upgrade to 0.23.35 or later

  ```sh
  # set org.http4s:http4s-ember-core_3 to 0.23.35 in your pom.xml or build.gradle
  ```


## Technical details

The vulnerability is an HTTP request/response smuggling flaw (CWE-444) in Http4s Ember's chunk transfer coding decoder. The root cause is that the chunk size parser strips leading and trailing whitespace and accepts a leading + or - sign, deviating from RFC 9112 §7.1 which defines chunk-size as 1*HEXDIG (hex digits only). An intermediary (proxy, firewall) that interprets or rejects these non-conformant chunk sizes differently than Ember will misalign on request boundaries. Attack preconditions for the server path: (1) Ember-based server deployed behind a keep-alive intermediary, (2) intermediary forwards chunked bodies verbatim without re-encoding, (3) intermediary disagrees with Ember on the +/- prefix or whitespace handling. An unauthenticated remote attacker can smuggle a request through the intermediary to reach the origin server with attacker-chosen method and headers, bypassing front-end security controls, poisoning cached responses, or hijacking request queues. The client path (response smuggling) requires a malicious or compromised upstream server. Patches are available: 0.23.35 for the 0.23.x line and 1.0.0-M47 for the 1.0.0-M series.

## Affected products

- Http4s http4s-ember-core_2.12 <= 0.23.34
- Http4s http4s-ember-core_2.13 <= 0.23.34, >= 1.0.0-M1 to <= 1.0.0-M46
- Http4s http4s-ember-core_3 <= 0.23.34, >= 1.0.0-M1 to <= 1.0.0-M46

## Identifiers

- CVE-2026-69216
- GHSA-jrpm-956j-96jg

## Timeline

- 2026-09-15: disclosed: Vulnerability published to GitHub Advisory Database
- 2026-09-15: patched: Patches released: v0.23.35 and v1.0.0-M47

## References

- [https://api.github.com/users/ERobertGII](https://api.github.com/users/ERobertGII)
- [https://github.com/ERobertGII](https://github.com/ERobertGII)
- [https://api.github.com/users/ERobertGII/gists%7B/gist_id%7D](https://api.github.com/users/ERobertGII/gists%7B/gist_id%7D)
- [https://api.github.com/users/ERobertGII/repos](https://api.github.com/users/ERobertGII/repos)
- [https://avatars.githubusercontent.com/u/93225934?v=4](https://avatars.githubusercontent.com/u/93225934?v=4)
- [https://api.github.com/users/ERobertGII/events%7B/privacy%7D](https://api.github.com/users/ERobertGII/events%7B/privacy%7D)

## Related threats

- [Http4s Ember HTTP/2 frame buffering denial of service](https://junglewise.ai/threats/cve-2026-88975-http4s-ember-http-2-frame-buffering-denial-of-service)
- [Http4s Ember HTTP/2 unbounded continuation frame accumulation](https://junglewise.ai/threats/cve-2026-69218-http4s-ember-http-2-unbounded-continuation-frame-accumulation)
- [Http4s DigestAuth replay attack in authorization header](https://junglewise.ai/threats/cve-2026-69206-http4s-digestauth-replay-attack-in-authorization-header)
- [Http4s Ember HTTP request smuggling via Transfer-Encoding parsing](https://junglewise.ai/threats/cve-2026-69205-http4s-ember-http-request-smuggling-via-transfer-encoding-parsing)
- [Http4s Ember HTTP/2 stream limit enforcement bypass](https://junglewise.ai/threats/cve-2026-69203-http4s-ember-http-2-stream-limit-enforcement-bypass)