HashiCorp Consul CVE-2026-105608

Requires a valid Consul ACL token holding service:write permission on a service, so ACLs must be enabled and the attacker must already be an authenticated mesh participant - it is not anonymous. The affected deployment must be using Consul service mesh (Connect) and the attacker leverages the Envoy escape-hatch (custom bootstrap/proxy) configuration path, which is normally gated behind mesh:write. Limiting factors: authenticated low-privilege access is mandatory (PR:L), the target must run service mesh with ACL authorization, and there is no indication of user interaction or non-default configuration being required beyond mesh usage. Patching to Consul CE/Enterprise 2.1.0 or Enterprise 1.21.19 is the vendor-stated fix.

The CVSS 3.1 base score of 8.8 (AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) reflects a network-reachable, low-complexity issue, but the PR:L metric is the decisive qualifier: exploitation requires an authenticated Consul ACL token that already holds service:write permission, so this is a privilege-escalation / authorization-bypass problem among existing mesh participants rather than an anonymous remote compromise. The vuln.today decision label is 'this_week', which indicates meaningful but non-emergency urgency. No EPSS score, no CISA KEV listing, and no verified exploit code are present in the supplied data - the only reference is the HashiCorp HCSEC-2026-47 advisory, so exploitation status is 'no public exploit identified at time of analysis'. CWE-178 (Improper Handling of Case Sensitivity) is listed and would point to a permission-string comparison flaw, but the advisory text does not describe the trigger, so the mechanism is not confirmed. Net assessment: this is a genuine, vendor-confirmed authorization bypass worth prioritizing for environments running Consul service mesh with ACLs, but the required service:write privilege and absence of any exploitation signal (no KEV, no EPSS, no working PoC) place it below drop-everything emergency status - consistent with the 'this_week' label.

An attacker or malicious insider who already holds a Consul ACL token scoped with service:write for a single service registers or updates that service's mesh sidecar proxy, embedding Envoy escape-hatch configuration that should require the higher mesh:write permission. Because the authorization check is bypassed, the low-privileged token is able to inject arbitrary Envoy proxy configuration it was never authorized to set. No public exploit code is identified; only the HashiCorp advisory reference exists.