GHSA-p77j-4mvh-x3m3 · Severity: critical · Ecosystem: go — gRPC-Go has an authorization bypass via missing leading slash in :path
gRPC-Go is the Go language implementation of gRPC. Versions prior to 1.79.3 have an authorization bypass resulting from improper input validation of the HTTP/2 `:path` pseudo-header. The gRPC-Go server was too lenient in its routing logic, accepting requests where the `:path` omitted the mandatory leading slash (e.g., `Service/Method` instead of `/Service/Method`). While the server successfully routed these requests to the correct handler, authorization interceptors (including the official `grpc/authz` package) evaluated the raw, non-canonical path string. Consequently, "deny" rules defined using canonical paths (starting with `/`) failed to match the incoming request, allowing it to bypass the policy if a fallback "allow" rule was present. This affects gRPC-Go servers that use path-based authorization interceptors, such as the official RBAC implementation in `google.golang.org/grpc/authz` or custom interceptors relying on `info.FullMethod` or `grpc.Method(ctx)`; AND that have a security policy contains specific "deny" rules for canonical paths but allows other requests by default (a fallback "allow" rule). The vulnerability is exploitable by an attacker who can send raw HTTP/2 frames with malformed `:path` headers directly to the gRPC server. The fix in version 1.79.3 ensures that any request with a `:path` that does not start with a leading slash is immediately rejected with a `codes.Unimplemented` error, preventing it from reaching authorization interceptors or handlers with a non-canonical path string. While upgrading is the most secure and recommended path, users can mitigate the vulnerability using one of the following methods: Use a validating interceptor (recommended mitigation); infrastructure-level normalization; and/or policy hardening.
Conclusion & alert: CVE-2026-33186 is rated Moderate Risk (62.8/100): CVSS Critical severity, with medium exploitation likelihood (EPSS 1.56%). Core evidence: EPSS rose +1.04% over the last day, indicating growing attacker interest. Mandatory action: Review affected assets and schedule remediation.
Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.
EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).
| # | Date | Old EPSS score | New EPSS score | Delta (New - Old) |
|---|---|---|---|---|
| 1 | 2026-07-16 | 0.52% | 1.56% | +1.04% |
| 2 | 2026-07-15 | 1.56% | 0.52% | -1.04% |
| 3 | 2026-06-30 | — | 1.56% | — |
Full EPSS history (5 records total)
CVSS metrics for this CVE.
| Base score | Version | Severity | Vector | Exploitability | Impact | Score source |
|---|---|---|---|---|---|---|
| 9.1 | 3.1 | CRITICAL |
|
3.9 | 5.2 | [email protected] |
| 9.1 | 3.1 | CRITICAL |
|
3.9 | 5.2 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c |
GHSA-p77j-4mvh-x3m3 · Severity: critical · Ecosystem: go — gRPC-Go has an authorization bypass via missing leading slash in :path
| vendor | priority | summary | link |
|---|---|---|---|
alpine
|
— | CVE-2026-33186: 1 source package rows (grpc); 19 state rows across 2 repos (3.23-community, edge-community); fixed 0, open 19. | https://security.alpinelinux.org/vuln/CVE-2026-33186 |
debian
|
not yet assigned | CVE-2026-33186 not yet assigned priority: Debian including 1 source packages (golang-google-grpc), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): open 3, resolved 2. | https://security-tracker.debian.org/tracker/CVE-2026-33186 |
redhat
|
high | — | https://access.redhat.com/security/cve/CVE-2026-33186 |
suse
|
high | CVE-2026-33186 severity important: SUSE including 367 source package names (amazon-cloudwatch-agent-1.300064.0-2.1, amazon/suse-sles-15-sp1-chost-byos-v20210304-hvm-ssd-x86_64, …), 662 product×package rows across 38 product lines (Image SLES12-SP5-GCE-SAP-BYOS, Image SLES12-SP5-GCE-SAP-On-Demand, … (38 product lines)): Known Not Affected 296, Known Affected 231, Fixed 66, Will Not Fix 53, First Fixed 16. | https://www.suse.com/security/cve/CVE-2026-33186/ |
ubuntu
|
high | CVE-2026-33186 high priority: Ubuntu including 2 source packages (golang-google-grpc, google-guest-agent), 14 status rows across 7 suites (bionic, focal, jammy, noble, questing, upstream, xenial): needs-triage 14. | https://ubuntu.com/security/CVE-2026-33186 |