CVE-2026-53602

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CVE-2026-53602

Summary: nebula-mesh - Host revocation is not durable: blocked/offboarded hosts can regain a valid certificate

Details: nebula-mesh is a self-hosted control plane for Slack Nebula mesh VPN. Prior to version 0.3.7, two related authorization gaps let a host that should no longer be trusted obtain a fresh, valid Nebula certificate, because nebula-mgmt does not re-evaluate revocation/authorization state at certificate issuance time — only at poll time. Firstly, the blocklist is not enforced at sign / re-enroll time. internal/api/enroll.go:128 calls caMgr.Sign(...) without consulting the blocklist. The blocklist is only checked in the poll path (internal/api/updates.go:57, fingerprintInBlocklist). The blocklist is keyed by certificate fingerprint (internal/store/sqlite.go), so a re-enrollment produces a new fingerprint that is not in the blocklist. Secondly, renewal does not re-validate operator / CA status. Auto-renewal at poll time (internal/api/updates.go:285-319, signHostCert) reads host.Name, host.Groups, host.NebulaIPs from the DB and re-signs without checking whether the owning operator is still active or the CA still valid. DisableOperator (internal/store/sqlite_operators.go) revokes sessions and API keys but does not retire the operator's CAs, and pki/signer.go checks only CA cert time-expiry, not operator/CA status. This issue has been patched in version 0.3.7.

References: https://github.com/forgekeep/nebula-mesh/releases/tag/v0.3.7, https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/53xxx/CVE-2026-53602.json, https://github.com/forgekeep/nebula-mesh/security/advisories/GHSA-339v-266x-79xr, https://nvd.nist.gov/vuln/detail/CVE-2026-53602, https://github.com/forgekeep/nebula-mesh/issues/178