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gRPC-Go CVE-2026-84303

| EUVDEUVD-2026-69419 MEDIUM
Improper Handling of Case Sensitivity (CWE-178)
2026-09-01 GitHub_M GHSA-qc2q-p7wx-3px3
Medium
Disputed · 6.3 Vendor: GitHub_M
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Severity by source

Sources disagree (Medium–Critical)
Vendor (GitHub_M) PRIMARY
6.3 MEDIUM
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
vuln.today AI
4.8 MEDIUM

AC:H reflects the specific precondition that DENY policies must use mixed-case header names; attacker needs no privileges since the flaw is in server-side policy evaluation.

3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
4.0 AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
SUSE
9.1 CRITICAL
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

vuln.today treats the vendor’s rating as authoritative. A higher third-party CVSS (e.g. CISA-ADP) is shown for transparency but does not drive the headline severity.

CVSS VectorVendor: GitHub_M

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
X

Lifecycle Timeline

3
Patch available
Sep 01, 2026 - 20:03 EUVD
Source Code Evidence Fetched
Sep 01, 2026 - 18:46 vuln.today
Analysis Generated
Sep 01, 2026 - 18:46 vuln.today

DescriptionCVE.org

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.

AnalysisAI

Authorization bypass in gRPC-Go's xDS RBAC HTTP filter prior to v1.83.1 allows network attackers to evade DENY policies when header matcher names use mixed case. Because gRPC metadata keys are always lowercased at the protocol layer, a DENY rule configured with canonical HTTP capitalization (e.g., X-Role, User-Agent) never fires, causing the policy to fail open and permit requests it should block. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

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Vulnerability AssessmentAI

Exploitation Exploitation requires three concurrent conditions: (1) the gRPC-Go server is configured to use the xDS RBAC HTTP filter via an xDS control plane (a service mesh deployment mode, not the default); (2) at least one RBAC DENY policy contains a header matcher whose name includes one or more uppercase characters (e.g., `X-Role`, `User-Agent`, `Host`); and (3) the attacker sends a request that would be matched by that rule if correctly normalized. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The CVSS 4.0 score of 6.3 with vector AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L accurately reflects the security posture. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario Full exploit scenario with step-by-step reproduction available after sign-in.
Remediation Upgrade gRPC-Go to version 1.83.1, which is the vendor-confirmed patched release (https://github.com/grpc/grpc-go/releases/tag/v1.83.1). … Detailed patch versions, workarounds, and compensating controls in full report.

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Vendor StatusVendor

SUSE

Severity: Critical
Product Status
SUSE Linux Enterprise Micro 5.5 Affected
SUSE Linux Enterprise Module for Containers 15 SP7 Affected
SUSE Linux Enterprise Module for Package Hub 15 SP7 Affected
SUSE Linux Enterprise Server 15 SP7 Affected
SUSE Linux Enterprise Server 16.0 Affected

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CVE-2026-84303 vulnerability details – vuln.today

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