CVE-2026-61699

### Summary nebula-mesh revokes a host by adding its certificate fingerprint to a per-CA blocklist and shipping that list to every other agent on each poll. Slack's Nebula enforces certificate revocation ONLY through the `pki.blocklist` list in `config.yml` (no CRL/OCSP). The project's own code states this: `internal/pki/durations.go:15` — "Revocation via the blocklist remains the immediate security control." The server side is fully implemented (computes per-CA blocklist via `GetBlocklistForCA`, returns it in the agent-updates response, sets `has_updates=true` when non-empty). The agent side was never implemented: 1. The agent decodes the `blocklist` JSON field into `UpdatesResponse.Blocklist` (`internal/agent/poller.go:33`) and then DISCARDS it — `poll()` applies `CertificatePEM`, `CACertPEM`, `ConfigYAML`, but never references `updates.Blocklist` (`internal/agent/poller.go:300-339`). 2. The config generator has NO field to emit `pki.blocklist` — `pkiSection` is only `ca`/`cert`/`key` (`internal/configgen/marshal.go:42-46`) and `GeneratorInput` carries no blocklist (`internal/configgen/generator.go:23-52`). So even the server-rendered `config.yml` shipped via `ConfigYAML` cannot carry it. Result: a blocked/offboarded/compromised host's certificate is never rejected by its peers. Its handshakes keep succeeding for the full remaining cert lifetime — up to 30 days for agent hosts (`DefaultAgentCertDuration`) and 365 days for mobile hosts (`DefaultMobileCertDuration`). Blocking a host in the UI/API has no effect on the data plane. ### Affected components - Agent drops the blocklist: `internal/agent/poller.go:33` (decode target), `internal/agent/poller.go:300-339` (poll() applies cert/CA/config, never the blocklist). - Generator cannot emit it: `internal/configgen/marshal.go:42-46` (`pkiSection{CA,Cert,Key}`), `internal/configgen/generator.go:23-52` (`GeneratorInput` has no blocklist), `internal/api/enroll.go:255-330` (`renderHostConfig`, source of shipped Config