{"id":"CVE-2026-84303","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-84303","generatedAt":"2026-10-28T08:27:39.355Z","title":"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.","description":"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.","published":"2026-09-01T19:17:31.000Z","lastModified":"2026-09-09T21:09:13.000Z","status":"Deferred","sourceIdentifier":"security-advisories@github.com","cvss":{"version":"4.0","score":6.3,"severity":"MEDIUM","vector":"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/M"},"cwe":["CWE-178","CWE-863"],"affected":[],"epss":{"score":0.00311,"percentile":0.23809,"date":"2026-10-27","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"low","text":"Lower severity and a low EPSS score (0.31%). Track it; it rarely justifies an emergency change on its own."},"changes":[],"references":[{"url":"https://github.com/grpc/grpc-go/commit/db9482836c298f234c896cf82ab68cafc78237f8","source":"security-advisories@github.com"},{"url":"https://github.com/grpc/grpc-go/commit/ebba6f3f1b206e2b4dc4d1d5a96d18430302c2fe","source":"security-advisories@github.com"},{"url":"https://github.com/grpc/grpc-go/pull/9332","source":"security-advisories@github.com"},{"url":"https://github.com/grpc/grpc-go/pull/9335","source":"security-advisories@github.com"},{"url":"https://github.com/grpc/grpc-go/releases/tag/v1.83.1","source":"security-advisories@github.com"},{"url":"https://github.com/grpc/grpc-go/security/advisories/GHSA-qc2q-p7wx-3px3","source":"security-advisories@github.com"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-84303","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}