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CVE-2026-84445 – Denial of Service (Server Crash) – grpc-go xDS Servers < 1.82.2 / 1.83.0–1.83.1

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Summary

CVE-2026-84445 is a denial-of-service vulnerability in grpc-go, the Go implementation of gRPC, affecting servers created with xds.NewGRPCServer(). A crafted request that omits both the :authority and Host headers triggers an index-out-of-bounds panic in the xDS routing interceptor, which is not recovered by the per-RPC goroutine and crashes the entire server process. The issue carries a CVSS score of 8.7 (High) and is remotely exploitable over the network.

Technical details

  • Root cause: Servers built with xds.NewGRPCServer() install an xDS routing interceptor on every RPC that looks up the request’s :authority header to select a virtual host. The HTTP/2 transport previously accepted requests lacking both :authority and Host headers, so the interceptor attempted to read the first element of an empty "authorities" slice, causing an index-out-of-bounds panic (CWE-129: Improper Validation of Array Index).
  • Uncaught exception: The per-RPC goroutine does not recover from this panic (CWE-248: Uncaught Exception), so the panic propagates and terminates the entire gRPC-Go server process rather than just the affected connection/RPC.
  • Trigger conditions: The target server must be configured with the xDS server API (xds.NewGRPCServer()); plain grpc.NewServer() deployments that do not register the xDS routing interceptor are not affected.
  • Attack vector: An attacker sends a crafted HTTP/2 request that omits both the :authority pseudo-header and the Host header. The transport-layer handshake (TLS, mTLS, or ALTS) must complete successfully before the request can reach the vulnerable routing logic — on insecure or standard-TLS deployments this requires no authentication, while mTLS/ALTS deployments require the attacker to already hold valid transport credentials.
  • Impact: Full denial of service — the crash affects the entire server process, not just a single connection, dropping all in-flight and future RPCs until the process is restarted.

Affected software

  • google.golang.org/grpc (grpc-go): versions prior to 1.82.2, and versions 1.83.0 up to (and including) 1.83.1, when the xDS server API (xds.NewGRPCServer()) is used.

Severity

  • CVSS Score: 8.7 (High)
  • CVSS Vector (v4.0): CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
  • Network attack vector, low attack complexity, no privileges or user interaction required; impact is limited to availability (High), with no confidentiality or integrity impact.

Mitigation and recommended actions

  • Immediate: Upgrade grpc-go to version 1.82.2 (for the 1.82.x branch) or 1.83.2 (for the 1.83.x branch), both of which reject requests missing both :authority and Host headers early in the HTTP/2 transport layer, consistent with other gRPC implementations.
  • If immediate patching isn’t possible: There are no documented workarounds; teams using xds.NewGRPCServer() should restrict network exposure of xDS-enabled gRPC endpoints (e.g., via network segmentation, mTLS/ALTS enforcement, or firewall rules limiting access to trusted clients) until the upgrade can be applied, and should monitor for unexpected server process restarts/crashes as a possible indicator of exploitation attempts.
  • Review dependency manifests and container images for transitive use of google.golang.org/grpc in services that configure xDS-based gRPC servers, since the vulnerability has driven dependency updates across many downstream Go projects.

References

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