CVE-2026-88975
Http4s: Ember HTTP/2 buffers a frame's declared payload before checking SETTINGS_MAX_FRAME_SIZE
Impact
Http4s is a Scala interface for HTTP services. Prior to 0.23.37 and 1.0.0-M48, Ember’s HTTP/2 read loop parses a frame’s 24-bit declared length but waits to buffer the entire payload before comparing it with SETTINGS_MAX_FRAME_SIZE. An unauthenticated peer can declare a payload near 16 MiB on a connection where Ember advertised 16 KiB and either complete or slowly stream it, causing up to 1024-fold memory amplification per connection before processFrame can reject the frame. The shared H2Connection.readLoop affects withHttp2 servers and clients, while HTTP/2-disabled configurations are unaffected, and the patch rejects oversized frames before buffering their payloads. This issue is fixed in versions 0.23.37 and 1.0.0-M48.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| maven | org.http4s:http4s-ember-core_2.13 | <= 0.23.36 | 0.23.37 |
| maven | org.http4s:http4s-ember-core_2.12 | <= 0.23.36 | 0.23.37 |
| maven | org.http4s:http4s-ember-core_3 | <= 0.23.36 | 0.23.37 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-gq9p-f254-h286
- https://github.com/http4s/http4s/security/advisories/GHSA-gq9p-f254-h286
- https://github.com/http4s/http4s/commit/87cf334fa3f608ef7d3eb359e71e037ba3336d29
- https://github.com/http4s/http4s/releases/tag/v0.23.37
- https://github.com/http4s/http4s/releases/tag/v1.0.0-M48