High, CVSS 7.5MavenPublished
blaze: Unbounded WebSocket message aggregation in http4s-blaze-server
CVE-2026-73493 · GHSA-7ppr-r889-mcf2
- Affected
- Maven org.http4s:http4s-blaze-server_3 >= 1.0.0-M1, < 1.0.0-M42
- Fixed in
- 1.0.0-M42· Vendor fix available
- Issue
- http4s-blaze-server aggregates the fragments of an incoming WebSocket message with no limit on total size or fragment count. A client that completes a WebSocket handshake can send an unterminated fragmented message and drive unbounded heap growth in the server JVM, resulting in denial of service via OutOfMemoryError. Impact Any http4s application serving WebSocket routes over BlazeServerBuilder is affected; no non-default configuration is required, and maxWebSocketBufferSize does not bound the aggregate (it bounds only individual frames). A single connection sending continuation frames that never set FIN forces the server to buffer every fragment until the heap is exhausted, terminating the JVM with OutOfMemoryError on the blaze selector thread. Small fragments amplify the cost through per-frame object overhead, so a modest volume of wire bytes is sufficient. Where the WebSocket endpoint is reachable without authentication the attacker is unauthenticated and remote; where the…
Recommended action: Upgrade to 1.0.0-M42 (pre-release) or later, then redeploy and verify.A vendor fix does not resolve your finding until you verify it in your own systems.