CVE-2026-73493
CVE-2026-73493 updated by NVD
Summary
Http4s (http4s-blaze-server) is a minimal, idiomatic Scala interface for HTTP services. Prior to 0.23.18 and 1.0.0-M42, http4s-blaze-server aggregates 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 through OutOfMemoryError. Any http4s application serving WebSocket routes over BlazeServerBuilder is affected, no non-default configuration is required, and maxWebSocketBufferSize does not bound the aggregate because 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. This issue is fixed in versions 0.23.18 and 1.0.0-M42.
Affected packages
| Ecosystem | Package | Affected versions | Fixed versions |
|---|---|---|---|
| Maven | org.http4s:http4s-blaze-server_2.12 | — | 0.23.18 |
| Maven | org.http4s:http4s-blaze-server_2.13 | — | 0.23.18, 1.0.0-M42 |
| Maven | org.http4s:http4s-blaze-server_3 | — | 1.0.0-M42 |
Remediation: Upgrade to 0.23.18 or later.
References
Includes data from the GitHub Advisory Database, licensed under CC-BY 4.0.
Includes data from the National Vulnerability Database (NIST). NVD data is in the public domain; this page is not endorsed by NIST.
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EPSS scores provided by the FIRST.org Exploit Prediction Scoring System.