nebula-mesh is a self-hosted control plane for Slack Nebula mesh VPN. Prior to version 0.7.1, revocation is the only in-band mechanism that isolates a compromised/offboarded host from a Nebula mesh. Because the blocklist never reaches any peer's config.yml, a Blocked host retains full overlay reachability to every peer under its CA (and internal services on the mesh) for up to 30d (agent) / 365d (mobile). An attacker who exfiltrates host.key+host.crt can run stock slackhq/nebula directly, ignore the agent's 403/410 poll responses, and stay connected after the operator revokes the host. Operator-visible state (UI shows blocked, audit log records it) is misleading. This issue has been patched in version 0.7.1.

CVE-2026-61699 affects nebula-mesh, a self-hosted control plane for Slack Nebula mesh VPN, in versions prior to 0.7.1. The vulnerability stems from a flawed revocation mechanism where blocklist entries are never propagated to peers' config.yml files. This allows a blocked or offboarded host to retain full overlay network reachability for up to 30 days (agent) or 365 days (mobile). An attacker who has exfiltrated a host's private key and certificate can bypass the revocation by running the stock Nebula client and ignoring 403/410 HTTP responses from the control plane. The operator-facing UI falsely shows the host as blocked, creating a misleading security posture. The vulnerability enables persistent unauthorized access to internal mesh services even after explicit revocation. A patch has been issued in version 0.7.1 of nebula-mesh.