What is CVE-2026-69203?

CVE-2026-69203 is a high-severity uncontrolled resource consumption 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. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.

How severe is CVE-2026-69203?

CVE-2026-69203 has a CVSS score of 7.5 (High). 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-2026-69203?

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-2026-69203?

Yes. CVE-2026-69203 is fixed in 0.23.35, 1.0.0-M47. Upgrade to this version or later.

Is CVE-2026-69203 exploitable, and should I be worried?

Whether CVE-2026-69203 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.

What actually determines whether CVE-2026-69203 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.

CVE-2026-69203 in org.http4s:http4s-ember-core_2.12

Q: How severe is CVE-2026-69203?

CVE-2026-69203 has a CVSS score of 7.5 (High). 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.

Q: Which packages are affected by CVE-2026-69203?

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.

Q: Is there a fix for CVE-2026-69203?

Yes. CVE-2026-69203 is fixed in 0.23.35, 1.0.0-M47. Upgrade to this version or later.

Q: Is CVE-2026-69203 exploitable, and should I be worried?

Whether CVE-2026-69203 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.

Q: What actually determines whether CVE-2026-69203 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.

Q: How do I fix CVE-2026-69203?

Upgrade: 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.

Summary

Http4s Ember HTTP/2 does not enforce SETTINGSMAXCONCURRENT_STREAMS

An ember server with HTTP/2 enabled (.withHttp2) does not enforce SETTINGS_MAX_CONCURRENT_STREAMS on streams opened by the peer. A single unauthenticated connection can open an unbounded number of concurrent streams, each of which allocates per-stream server state that is never released, exhausting the heap.

Preconditions

Server: with .withHttp2 enabled.
Client: makes HTTP/2 requests to malicious or compromised sites. enablePush is not enforced.

Workarounds

Disable HTTP/2 on EmberServerBuilder or EmberClientBuilder (default)
Client only: avoid HTTP/2 to untrusted servers until patched.

Impact

Unauthenticated remote denial of service (memory exhaustion) against any Ember server built .withHttp2. This is the resource-exhaustion class of the HTTP/2 "Rapid Reset" family (CVE-2023-44487).

The same unchecked allocation path is reachable on the client via server-initiated PUSH_PROMISE frames, so a malicious or compromised server can exhaust an ember-client's heap the same way.

Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.

CVE-2026-69203 has a CVSS score of 7.5 (High). 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

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.

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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

What is CVE-2026-69203? CVE-2026-69203 is a high-severity uncontrolled resource consumption 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. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
How severe is CVE-2026-69203? CVE-2026-69203 has a CVSS score of 7.5 (High). 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-2026-69203?
- 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-2026-69203? Yes. CVE-2026-69203 is fixed in 0.23.35, 1.0.0-M47. Upgrade to this version or later.
Is CVE-2026-69203 exploitable, and should I be worried? Whether CVE-2026-69203 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-2026-69203 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-2026-69203?
- 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