{"cve":"CVE-2026-73493","nvd":{"published":"2026-08-12T22:17:16.673","modified":"2026-10-24T15:10:00.190","status":"Awaiting Analysis","description":"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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5},"cwes":["CWE-770"],"references":["https://github.com/http4s/blaze/commit/173e8ca820a0d12110bfe409c72e9b9c3d28d471","https://github.com/http4s/blaze/releases/tag/v0.23.18","https://github.com/http4s/blaze/releases/tag/v1.0.0-M42","https://github.com/http4s/blaze/security/advisories/GHSA-7ppr-r889-mcf2"],"products":[],"source":"nvd","synced_at":"2026-10-24T16:53:35.584907681+00:00"},"epss":{"cve":"CVE-2026-73493","score":0.0063,"percentile":0.49874,"date":"2026-10-25"},"kev":null,"osv":[{"id":"GHSA-7ppr-r889-mcf2","url":"https://osv.dev/vulnerability/GHSA-7ppr-r889-mcf2","summary":"blaze: Unbounded WebSocket message aggregation in http4s-blaze-server","modified":"2026-08-12T21:25:59.207322Z","packages":[{"ecosystem":"Maven","name":"org.http4s:http4s-blaze-server_2.13","purl":"pkg:maven/org.http4s/http4s-blaze-server_2.13","ranges":["<0.23.18"],"fixed":["0.23.18"]},{"ecosystem":"Maven","name":"org.http4s:http4s-blaze-server_2.13","purl":"pkg:maven/org.http4s/http4s-blaze-server_2.13","ranges":[">=1.0.0-M1 <1.0.0-M42"],"fixed":["1.0.0-M42"]},{"ecosystem":"Maven","name":"org.http4s:http4s-blaze-server_2.12","purl":"pkg:maven/org.http4s/http4s-blaze-server_2.12","ranges":["<0.23.18"],"fixed":["0.23.18"]},{"ecosystem":"Maven","name":"org.http4s:http4s-blaze-server_3","purl":"pkg:maven/org.http4s/http4s-blaze-server_3","ranges":[">=1.0.0-M1 <1.0.0-M42"],"fixed":["1.0.0-M42"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}