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Vulnerabilities

Vulnerability · CVE-2026-33186

gRPC-Go is the Go language implementation of gRPC.

Published Mar 20, 2026 · catalog updated Sep 18, 2026 · Red Hat

Check if you run it

No confirmed exploitation is on record for CVE-2026-33186. EPSS is 1.69%. Act only if a listed version of Red Hat is installed.

Severity
Critical9.1
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
1.69%
Remediation
Fix linked
Affected products
cpe grpc/grpc

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 pseudo-header. The gRPC-Go server was too lenient in its routing logic, accepting requests where the omitted the mandatory leading slash (e.g., instead of ). While the server successfully routed these requests to the correct handler, authorization interceptors (including the official 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 or custom interceptors relying on or ; 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 headers directly to the gRPC server. The fix in version 1.79.3 ensures that any request with a that does not start with a leading slash is immediately rejected with a 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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

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  • cpe grpc/grpcversion unspecified

How to fix CVE-2026-33186

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-33186. EPSS is 1.69%. Act only if a listed version of Red Hat is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-285: Improper Authorization; CWE-551. EPSS 1.69%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Related Odoo Git fixes

Quoted Community commit messages that cite this CVE. Presence of a commit is not proof that every edition or backport includes the fix. Enterprise proprietary diffs are never shown here. Timeline

  • Jul 20, 2026 · referenced

    Update google.golang.org/grpc to v1.82.1

    Update google.golang.org/grpc to v1.82.1 This release fixes three security issues in grpc-go. - A gRPC server now stops reading from a connection when a peer sends too many HTTP/2 control frames. Before this change, a peer could flood a server with control frames and make it use too much memory and CPU. See grpc/grpc-go#9236. There is no fixed v1.81.x release. - The GRPC_GO_EXPERIMENTAL_DISABLE_STRICT_PATH_CHECKING environment variable is removed. Setting it turned strict path checking off and brought back the authorization bypass from CVE-2026-33186. - The old gzip Decompressor API now limits how much data it decompresses, so a small compressed message can no longer use an unbounded amount of memory. Kubernetes does not call this API. The update does not change any other dependency. Kubernetes already requires newer versions of everything grpc v1.82.1 needs, so the vendor cha…
    https://github.com/kubernetes/kubernetes/commit/bf2712d71b395db54097b5ae40f1383fe979e384

Timeline

Detection, updates, and resolution for this record.

  1. Mar 20, 2026 · NIST NVD

    Detected

    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 pseudo-header. The gRPC-Go server was too lenient in its routing logic, accepting requests where the omitted the mandatory leading slash (e.g., instead of ). While the server successfully routed these requests to the correct handler, author

  2. Sep 18, 2026 · NIST NVD

    Updated

    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 pseudo-header. The gRPC-Go server was too lenient in its routing logic, accepting requests where the omitted the mandatory leading slash (e.g., instead of ). While the server successfully routed these requests to the correct handler, author

Sources

  • CSAF AdvisoriesVendor advisoryRHSA-2026:9872:CVE-2026-33186

    A flaw was found in gRPC-Go, the Go language implementation of gRPC. This vulnerability, an authorization bypass, is caused by improper input validation of the HTTP/2 pseudo-header. A remote attacker can exploit this by sending raw HTTP/2 frames with a malformed that omits the ma

    security.access.redhat.com
  • CVE.orgVulnerability recordCVE-2026-33186

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-33186

    30-day exploitation probability 1.7%

    first.org
  • NIST NVDVulnerability recordCVE-2026-33186

    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 pseudo-header. The gRPC-Go server was too lenient in its routing logic, accepting requests where the omi

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.