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Fencer Vulns
medium 6.3

CVE-2026-84303 json

gRPC-Go: xDS RBAC HTTP Filter bypass via mixed-case Header Matching and gRFC A41 validation evasion

published 2026-09-01 2 mo ago modified 2026-09-15 54 d ago also GHSA-qc2q-p7wx-3px3 , GO-2026-6441 , EUVD-2026-69419

cvss
6.3
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 24%
public exploits
0
none known

Summary

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.

Patch / fix

  • go google.golang.org/grpc 1.83.1
  • terraform-provider-aws SLE Module for Public Cloud 15 SP5, SLE Module for Public Cloud 15 SP4 3.11.0-150200.6.29.2
  • terraform-provider-tls SLE Module for Public Cloud 15 SP5, SLE Module for Public Cloud 15 SP4 3.0.0-150200.5.26.2
  • terraform-provider-helm SLE Module for Public Cloud 15 SP5, SLE Module for Public Cloud 15 SP4 2.9.0-150200.6.34.2
  • terraform-provider-null SLE Module for Public Cloud 15 SP5, SLE Module for Public Cloud 15 SP4 3.0.0-150200.6.32.2
  • terraform-provider-local SLE Module for Public Cloud 15 SP5, SLE Module for Public Cloud 15 SP4 2.0.0-150200.6.30.2
  • terraform-provider-google SLE Module for Public Cloud 15 SP5, SLE Module for Public Cloud 15 SP4 3.43.0-150200.6.23.2
  • terraform-provider-random SLE Module for Public Cloud 15 SP5, SLE Module for Public Cloud 15 SP4 3.0.0-150200.6.26.2
  • terraform-provider-azurerm SLE Module for Public Cloud 15 SP5, SLE Module for Public Cloud 15 SP4 2.32.0-150200.6.23.2

suse advisories SUSE-SU-2026:4628-1SUSE-SU-2026:24150-1SUSE-SU-2026:4444-1SUSE-SU-2026:4389-1SUSE-SU-2026:4388-1SUSE-SU-2026:4308-1

  • rqlite openSUSE Leap 16.0 10.6.6-bp160.1.1
  • warewulf4 openSUSE Leap 16.0 4.7.1-bp160.2.1
  • warewulf4 openSUSE Tumbleweed 4.7.1-2.1
  • kubevirt1.8 openSUSE Tumbleweed 1.8.4-7.1
  • gh openSUSE Leap 16.0 2.102.0-bp160.1.1
  • alloy openSUSE Tumbleweed 1.20.1-1.1
  • amazon-ecs-init openSUSE Leap 16.0 1.107.0-160000.1.1
  • grafana openSUSE Tumbleweed 12.4.11-1.1

opensuse advisories openSUSE-SU-2026:22224-1openSUSE-SU-2026:22221-1openSUSE-SU-2026:12375-1openSUSE-SU-2026:12241-1openSUSE-SU-2026:22134-1openSUSE-SU-2026:12114-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-84303 updated cvss 6.5

github.com/grpc/grpc-go: gRPC-Go: RBAC policy bypass and validation evasion via mixed-case header matching

  • Red Hat OpenShift AI (RHOAI) rhoai/odh-mlflow-operator-rhel9, rhoai/odh-mod-arch-gen-ai-rhel9, rhoai/odh-workbenches-operator-rhel9, rhoai/odh-model-registry-operator-rhel9, rhoai/odh-kuberay-operator-controller-rhel9
    affected: no fix available “Fix deferred”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
2 mo ago

Exploit prediction

0.31% chance of exploitation in the next 30 days, higher than 24% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 4.0 6.3 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
CNA 4.0 6.3 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

Affected packages

ecosystem package affected fixed in
go google.golang.org/grpc
<1.83.1
1.83.1

Affected products

  • grpc grpc-go

Classification

Weakness
  • CWE-178 Improper Handling of Case Sensitivity
  • CWE-863 Incorrect Authorization

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.