Summary
Http4s: Ember chunk parser lenience (TE.TE request smuggling)
Ember's chunk decoder parses the size token leniently: it strips leading and trailing whitespace and accepts a leading + or - sign. RFC9112 §7.1 defines chunk-size = 1*HEXDIG. An intermediary that parses the chunk boundary differently (or rejects it) will disagree with Ember on request framing, enabling HTTP request smuggling (TE.TE).
Server
Request smuggling (TE.TE) when ember-server is an origin behind an intermediary that forwards the body verbatim but interprets the malformed chunk sizes differently
- Front-end security bypass: the smuggled request reaches paths the intermediary might have blocked, with attacker-chosen method and headers.
- Cache poisoning: the smuggled response is associated with the next request key in a caching proxy.
- Request queue hijack:
Client
ember-client has the same leniencies on the response path, which enables response smuggling when http4s is used as a gateway. This is less severe, as it requires a malicious or compromised upstream rather than an anonymous remote client.
Preconditions
- Unauthenticated remote attacker (server)
- ember-server as origin behind a keep-alive intermediary
- Malicious or compromised upstream (client)
- Intermediary or upstream forwards chunked bodies without re-encoding and disagrees with Ember on
+prefix,-prefix, or leading and trailing octets rather than rejecting.
Workarounds
- Intermediary strictly rejects malformed chunk sizes
- Intermediary buffers and re-encodes request bodies
References
Impact
CVE-2026-69216 has a CVSS score of 5.4 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.23.35, 1.0.0-M47); upgrading removes the vulnerable code path.
Affected versions
Security releases
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.
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See it in your environmentNew to Kodem? Get a demo →Remediation advice
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
- What is CVE-2026-69216? CVE-2026-69216 is a medium-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.
- How severe is CVE-2026-69216? CVE-2026-69216 has a CVSS score of 5.4 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which packages are affected by CVE-2026-69216?
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)
- Is there a fix for CVE-2026-69216? Yes. CVE-2026-69216 is fixed in 0.23.35, 1.0.0-M47. Upgrade to this version or later.
- Is CVE-2026-69216 exploitable, and should I be worried? Whether CVE-2026-69216 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
- What actually determines whether CVE-2026-69216 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.
- How do I fix CVE-2026-69216?
- Upgrade
org.http4s:http4s-ember-core_2.12to 0.23.35 or later - Upgrade
org.http4s:http4s-ember-core_2.13to 0.23.35 or later - Upgrade
org.http4s:http4s-ember-core_3to 0.23.35 or later - Upgrade
org.http4s:http4s-ember-core_2.13to 1.0.0-M47 or later - Upgrade
org.http4s:http4s-ember-core_3to 1.0.0-M47 or later
- Upgrade