CVE-2026-105608

A flaw was found in HashiCorp Consul. An authenticated user with service write permissions can bypass authorization controls during service mesh proxy registration. By applying custom Envoy proxy configurations without possessing required mesh write privileges, an attacker can alter proxy settings beyond their authorized scope, leading to privilege escalation.

Important: This flaw is assessed as having Important severity because authenticated actors possessing standard service registration permissions can circumvent authorization checks to inject arbitrary Envoy proxy settings, impacting the confidentiality and integrity of service mesh communications. Although exploitation requires existing service-level access, it exceeds expected privileges by modifying mesh-wide routing behavior without holding administrative credentials. In Red Hat Enterprise Linux environments, client integrations containing Consul libraries do not execute the affected Consul server service mesh registration service.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

--- CME Mitigation Guidance (2026-11-02) --- Disclaimer: The following mitigation solutions are provided as a courtesy, pending the application of an official patch. This content was generated utilizing AI tools in conjunction with data from https://cmetaxonomy.org. Customers are advised to independently evaluate and test these temporary mitigations within their own infrastructure.

The highest-value action is to enforce mesh:write authorization on all alternate key spellings and encodings during Consul service mesh proxy registration: upgrade to Consul Community Edition 2.1.0, Consul Enterprise 2.1.0 / 1.21.19 (or the fixed Grafana builds), which enforce mesh:write authorization checks across all alternate key spellings and encodings for Envoy escape-hatch configurations during proxy registration, closing all 2 injection vectors (crafted key spellings for Envoy escape-hatch configuration, alternate key encodings bypassing permission verification). Until patched, this is a concern on Consul service mesh deployments where authenticated users have service:write permissions on a proxy and destination service, so Restrict network access to the Consul service registration API and audit accounts holding service:write permissions on proxies and destination services. As a compensating measure, Detect unauthorized Envoy proxy configurations applied during service mesh proxy registration by flagging drift against declared IaC baselines and Capture and forward Consul service registration API calls to a SIEM to detect proxy registration payloads containing alternate escape-hatch keys. These controls limit blast radius and contain exploitation, but they do not fix the underlying authorization bypass defect — apply the upstream patch to fully remediate.

Highest-impact CME: CME-1007 Application Configuration Drift Detection (IaC Enforcement) (medium)