GHSA-9vwc-pc8p-253q
Http4s Ember HTTP/2 does not enforce SETTINGS_MAX_CONCURRENT_STREAMS
Packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| Maven | org.http4s:http4s-ember-core_2.12 | < 0.23.35 | 0.23.35 |
| Maven | org.http4s:http4s-ember-core_2.13 | < 0.23.35 | 0.23.35 |
| Maven | org.http4s:http4s-ember-core_3 | < 0.23.35 | 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 |
Details
As written in the advisory (Markdown source, shown as plain text).
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.
References
External links from the advisory. They lead to third-party sites.