CVE-2026-84303: Grpc Grpc-Go

Medium severity, CVSS 6.3. EPSS: 0.3% chance of exploitation in the next 30 days.

gRPC-Go is the Go language implementation of gRPC. Prior to 1.83.1, the xDS RBAC HTTP filter in internal/xds/httpfilter/rbac/rbac.go does not lowercase header matcher names in normalizeHeaderMatcher even though incoming metadata keys are lowercase. A DENY policy using a mixed-case name such as X-Role or User-Agent therefore does not match and fails open, allowing requests that should be rejected. The same case mismatch permits :Scheme or Grpc-Status to evade gRFC A41 validation and prevents Host from being rewritten to :authority. This issue is fixed in version 1.83.1.

Affected products

• Grpc Grpc-Go: before 1.83.1 (fixed in 1.83.1)

Published 2026-09-01. Last modified 2026-09-09.