CVE-2026-84303Network attack vectorHinoki check available

Authorization bypass via mixed-case header matcher

Published Sep 1, 2026 · Updated Sep 2, 2026

Authorization bypass in gRPC-Go before 1.83.1 allows remote attackers to evade xDS RBAC DENY rules through mixed-case header matchers. normalizeHeaderMatcher in internal/xds/httpfilter/rbac/rbac.go compares policy header names without lowercasing them, while incoming metadata keys are always lowercase. Exposure requires an xDS RBAC DENY policy that uses an uppercase header name; matching requests are served instead of rejected.

CVSS severity6.3
Medium
EPSS probability0.31%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Authorization bypass in gRPC-Go before 1.83.1 allows remote attackers to evade xDS RBAC DENY rules through mixed-case header matchers. normalizeHeaderMatcher in internal/xds/httpfilter/rbac/rbac.go compares policy header names without lowercasing them, while incoming metadata keys are always lowercase. Exposure requires an xDS RBAC DENY policy that uses an uppercase header name; matching requests are served instead of rejected.

The record

CVE
CVE-2026-84303
Published
Sep 1, 2026
Updated
Sep 2, 2026
Vendor
gRPC
Product
gRPC-Go
Classifications
CWE-178, CWE-863, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 1, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 2, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 1.83.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

gRPC · gRPC-Goversion=< 1.83.1

Published CVSS scores

8.2TenableCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N
6.3TenableCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-178Improper Handling of Case Sensitivity
CWE-863Incorrect Authorization
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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