CVE-2026-53602: nebula-mesh Host Revocation Is Not Durable Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-339v-266x-79xr",
  "modified" : "2026-07-09T20:52:27Z",
  "published" : "2026-07-09T20:52:27Z",
  "aliases" : [ "CVE-2026-53602" ],
  "summary" : "nebula-mesh: Host revocation is not durable - blocked/offboarded hosts can regain a valid certificate",
  "details" : "## Summary\n\nTwo 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.\n\n## 1. Blocklist not enforced at sign / re-enroll time\n\n`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.\n\n`mintEnrollmentTokenForHost` (`internal/api/hosts.go:491`) authorizes the caller via `canAccessHost` but does **not** check the host status. There is no guard preventing a `blocked` host from transitioning back to `enrolled` (`internal/store/sqlite.go`, `enrollHostInTx` updates status unconditionally).\n\n**Impact:** A host that an operator has blocked can be silently un-blocked by issuing a new enrollment token and re-enrolling — it receives a fresh certificate (new fingerprint) that passes all subsequent poll-time blocklist checks. Revocation is therefore not durable. Requires an operator action (minting a re-enroll token), so this is an integrity/operational-revocation failure rather than an unauthenticated bypass.\n\n## 2. Renewal does not re-validate operator / CA status\n\nAuto-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.\n\n**Impact:** A host enrolled under an operator who is later disabled continues to renew its certificate indefinitely. Offboarding an operator does not cut off the hosts they provisioned.\n\n## Affected versions\n\nLatest tagged release (v0.3.6) and `main`.\n\n## Remediation\n\n1. Call a blocklist/status guard inside `handleEnroll` and `signHostCert` **before** `caMgr.Sign(...)`; refuse issuance for a host whose status is `blocked` or whose previous fingerprint is on the blocklist. Require an explicit unblock before re-enroll.\n2. At renewal, re-resolve the owning operator/CA status and reject renewal if the operator is disabled or the CA retired (force re-enrollment instead).\n\n## Discovery\n\nFound during an internal source + offensive security audit (tracking issue #178). Adversarially cross-verified against the code paths above.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:U"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/forgekeep/nebula-mesh"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.3.7"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/forgekeep/nebula-mesh/security/advisories/GHSA-339v-266x-79xr"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/forgekeep/nebula-mesh/issues/178"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/forgekeep/nebula-mesh"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-613", "CWE-862" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-09T20:52:27Z",
    "nvd_published_at" : null
  }
}