Improper Handling of Case Sensitivity Affecting github.com/grpc/grpc-go/internal/xds/httpfilter/rbac package, versions <1.83.1
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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- published2 Sept 2026
- disclosed1 Sept 2026
- creditMarkus Magnuson
Introduced: 1 Sep 2026
NewCVE-2026-84303 Â (opens in a new tab)How to fix?
Upgrade github.com/grpc/grpc-go/internal/xds/httpfilter/rbac to version 1.83.1 or higher.
Overview
Affected versions of this package are vulnerable to Improper Handling of Case Sensitivity in the xDS RBAC HTTP filter, which unconditionally lowercases incoming metadata keys so a header matcher configured with uppercase letters, such as X-Role, never matches. An attacker can reach traffic that an RBAC policy was meant to deny, since the rule evaluates as a non-match and fails open, and can also smuggle reserved grpc--prefixed headers such as Grpc-Status past the case-sensitive gRFC A41 validation by altering their casing. This applies only where an operator has defined xDS RBAC policies with header matchers, and the policy bypass depends on those matchers using mixed-case header names.