CVE-2026-84303

MEDIUMPre-NVD 6.36.3—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 6.3 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3%, top 76% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Trending — 3 sources updated this week
6.3EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 6.3Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
6.3
EG Score
6.3(medium)
EG Risk
43(Track)
EG Risk 43/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity63% × 45%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
24%
KEV
Not listed

Published

September 1, 2026

Last Modified

September 9, 2026

Advisory Details (6)

Auto-updated Sep 1, 2026
Patch available. Sources: github, github_pr, github_commit, github_release.
github_release Patch Available

Release 1.83.1

Patch available: grpc/grpc-go v1.83.1

https://github.com/grpc/grpc-go/releases/tag/v1.83.1
github_commit Patch Available

commit ebba6f3f1b20 (grpc/grpc-go)

Patch available: grpc/grpc-go v1.83.1 (contains commit ebba6f3f1b20)

https://github.com/grpc/grpc-go/commit/ebba6f3f1b206e2b4dc4d1d5a96d18430302c2fe
github_commit

commit db9482836c29 (grpc/grpc-go)

Fix landed in grpc/grpc-go commit db9482836c29 — awaiting tagged release

https://github.com/grpc/grpc-go/commit/db9482836c298f234c896cf82ab68cafc78237f8
github_pr Patch Available

Cherry-pick #9258 and #9332 into v1.83.x

Patch available: grpc/grpc-go v1.83.1 (PR #9335 merged 2026-08-19)

https://github.com/grpc/grpc-go/pull/9335
github_pr

xds/rbac: lowercase header matcher names before matching

Fix merged in grpc/grpc-go PR #9332 on 2026-08-19 — awaiting tagged release

https://github.com/grpc/grpc-go/pull/9332
github Patch Available

xDS RBAC HTTP Filter bypass via mixed-case Header Matching and gRFC A41 validation evasion · Advisory · grpc/grpc-go · GitHub

https://github.com/grpc/grpc-go/security/advisories/GHSA-qc2q-p7wx-3px3

Vendor Advisories for CVE-2026-84303(2)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(4 across 4 ecosystems)
Debian:12(1)
PackageVulnerable rangeFixed inDependents
golang-google-grpc1.33.3-2 ... 1.81.1-1 (24 versions)——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
golang-google-grpc1.64.0-7 ... 1.81.1-1 (7 versions)——
Debian:14(1)
PackageVulnerable rangeFixed inDependents
golang-google-grpc1.64.0-7 ... 1.81.1-1 (7 versions)——
Go(1)
PackageVulnerable rangeFixed inDependents
google.golang.org/grpc—1.83.1—

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 19× in last 7d / 40× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-09-19 08:07 UTCEG score recompute
  2. 2026-09-19 08:07 UTCVendor advisory
  3. 2026-09-18 19:28 UTCEPSS rescore
  4. 2026-09-18 06:56 UTCEG score recompute
  5. 2026-09-18 06:56 UTCVendor advisory
  6. 2026-09-17 19:32 UTCEPSS rescore
  7. 2026-09-17 05:45 UTCEG score recompute
  8. 2026-09-17 05:45 UTCVendor advisory
  9. 2026-09-16 14:09 UTCEPSS rescore
  10. 2026-09-16 05:15 UTCEPSS rescore
  11. 2026-09-16 04:30 UTCEG score recompute
  12. 2026-09-16 04:30 UTCVendor advisory
  13. 2026-09-15 03:12 UTCEPSS rescore
  14. 2026-09-15 03:12 UTCEPSS rescore
  15. 2026-09-15 03:10 UTCVendor advisory
  16. 2026-09-14 01:57 UTCEG score recompute
  17. 2026-09-14 01:57 UTCVendor advisory
  18. 2026-09-13 00:46 UTCEG score recompute
  19. 2026-09-13 00:46 UTCVendor advisory
  20. 2026-09-11 23:34 UTCEG score recompute
  21. 2026-09-11 23:34 UTCVendor advisory
  22. 2026-09-11 14:53 UTCEPSS rescore
  23. 2026-09-11 14:53 UTCEPSS rescore
  24. 2026-09-10 22:22 UTCEG score recompute
  25. 2026-09-09 21:11 UTCVendor advisory
Show 15 more
  1. 2026-09-09 04:20 UTCEG score recompute
  2. 2026-09-09 04:20 UTCVendor advisory
  3. 2026-09-08 22:01 UTCEPSS rescore
  4. 2026-09-07 01:56 UTCEG score recompute
  5. 2026-09-06 13:48 UTCEPSS rescore
  6. 2026-09-06 00:40 UTCEG score recompute
  7. 2026-09-05 15:31 UTCEPSS rescore
  8. 2026-09-04 23:27 UTCEG score recompute
  9. 2026-09-04 05:07 UTCEPSS rescore
  10. 2026-09-02 20:22 UTCEG score recompute
  11. 2026-09-02 19:28 UTCEG score recompute
  12. 2026-09-02 14:12 UTCEPSS rescore
  13. 2026-09-01 19:30 UTCEG score recompute
  14. 2026-09-01 18:23 UTCEG score recompute
  15. 2026-09-01 18:22 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-84303?
CVE-2026-84303 is a medium vulnerability published on September 1, 2026. 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…
When was CVE-2026-84303 disclosed?
CVE-2026-84303 was first published in the National Vulnerability Database on September 1, 2026, with the most recent update on September 9, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-84303 actively exploited?
CVE-2026-84303 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 75.9% of all scored CVEs.
What is the CVSS score of CVE-2026-84303?
CVE-2026-84303 has a CVSS v3 base score of 6.3 (NVD).
How do I remediate CVE-2026-84303?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-84303, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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