highCVSS 7.5Vulnerability

CVE-2026-69203

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. ## 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. ## 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.

Properties

ghsa_id
GHSA-9vwc-pc8p-253q
summary
Http4s Ember HTTP/2 does not enforce SETTINGS_MAX_CONCURRENT_STREAMS
severity
high
cvss_score
7.5
cve_id
CVE-2026-69203
cvss_vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
signal_observed_at
2026-09-15T21:13:07+00:00
is_ghsa_only
false
ghsa_published
2026-09-15T19:53:14Z
source_url
https://github.com/advisories/GHSA-9vwc-pc8p-253q
ghsa_updated
2026-09-15T19:53:27Z

Related Entities (9)

REPORTED_BY (1)

[Source]GitHub Advisory Database

VULNERABLE_TO (3)

[Software]maven/org.http4s:http4s-ember-core_3
[Software]maven/org.http4s:http4s-ember-core_2.12
[Software]maven/org.http4s:http4s-ember-core_2.13

AFFECTS (3)

[Software]maven/org.http4s:http4s-ember-core_3
[Software]maven/org.http4s:http4s-ember-core_2.13
[Software]maven/org.http4s:http4s-ember-core_2.12

HAS_WEAKNESS (2)

[Weakness]Allocation of Resources Without Limits or Throttling
[Weakness]Uncontrolled Resource Consumption

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CVE-2026-69203 (CVSS 7.5) — Ninja Signal Threat Intelligence | Ninja Signal