9.1

CVE-2026-33186: gRPC-Go has an authorization bypass via missing leading slash in :path

Modified
AliasesSUSE-SU-2026:1194-1SUSE-SU-2026:1195-1SUSE-SU-2026:1197-1
Published 20-03-2026Last modified 18-09-2026

Vulnerability summary

CVE-2026-33186 is a critical (CVSS 9.1) Improper Authorization vulnerability in grpc. EPSS estimates a 1.58% chance of exploitation in the next 30 days, higher than 75.5% of scored vulnerabilities.

Priority
Prioritisesevere

Severe, CVSS 9.1 (CVE.org); no exploitation reported by the 5 checked sources; EPSS 2% (FIRST, 03-11-2026)

Source freshness unavailable

How is this decided?
CVSS score
9.1/10
010
Critical · v3.1 (CVE.org)
EPSS score
1.58%
0%100%
Low · -0.04 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 93 · Related 70
MGASA-2026-0147OPENSUSE-RU-2026:21160-1OPENSUSE-SU-2026:10601-1OPENSUSE-SU-2026:10613-1OPENSUSE-SU-2026:10618-1OPENSUSE-SU-2026:10631-1

Timeline

  1. 20-03-2026
    PublishedVulnerability first disclosed.
  2. 18-09-2026
    Last modifiedVulnerability information updated.

Description

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.

CVSS metrics

9 scores · 9 sources · 1 version

EPSS trend

Probability

1.58%

Chance of exploitation in the next 30 days

Percentile

76%

Versus all other CVEs

30-day change

Decrease -0.04 pp

From 1.63% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.

Chainguard199 products
  • aactl< 0.4.12-r47
  • agentbeat< 9.2.4-r6
  • agentbeat-fips< 9.2.4-r6
  • amazon-cloudwatch-agent< 1.300065.0-r1
  • amazon-cloudwatch-agent-fips< 1.300065.0-r1
Alpine1 product
  • rclone< 1.73.5-r0

2 vendors · 200 products · Showing 200 of 3471

References

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