{"id":"GHSA-7hp6-g3pq-3pc3","summary":"nebula-mesh: Host advanced overrides allow YAML injection into agent config.yml","details":"`internal/configgen/generator.go:86,108,119` interpolates the operator-supplied `ListenHost` and `TunDevice` fields raw into a `text/template` that produces the agent's `config.yml`. `internal/web/advanced.go:20-35` accepts both with only `strings.TrimSpace` — no character or shape validation.\n\n## Exploit\nAn operator (or attacker with any operator key, given the cross-tenant CRUD advisory) sets `adv_tun_device` to:\n\n```\nnebula0\nlighthouse:\n  am_lighthouse: true\n  hosts: [\"10.0.0.1\"]\n#\n```\n\nThe agent fetches the rendered config on its next signed poll. On config reload, it loads the injected YAML keys: the host self-promotes to lighthouse, attracts mesh traffic, or sets `am_relay: true` to be selected as a relay. The `ListenHost` field has the same shape.\n\n## Affected\nAll released versions prior to v0.3.2.\n\n## Threat model\n- **Today**: operator can compromise their own host's config (trivially allowed if they own the host, but they can also set lighthouse/relay flags that the operator-create form does NOT expose — privilege uplift within their own tenant).\n- **Combined with the critical /api/v1 authz advisory**: any operator key can mutate ANOTHER tenant's host overrides and inject YAML there.\n- **Post-fix of the authz advisory**: still relevant — the agent unconditionally trusts whatever config the server hands it, so any future operator-impersonation bug re-amplifies this.\n\n## Suggested fix\nTwo options, either acceptable:\n\n1. **Input validation** in `parseAdvancedFromForm` (`internal/web/advanced.go`):\n   - `ListenHost`: regex `^[A-Za-z0-9.:\\[\\]_-]+$` (IPv4/IPv6/hostname)\n   - `TunDevice`: regex `^[A-Za-z0-9_-]{1,15}$` (Linux IFNAMSIZ caps at 15)\n   Reject invalid input with a form-level error; do not write to the host row.\n\n2. **Safer marshalling**: switch `configgen/generator.go` to marshal a typed Go struct via `gopkg.in/yaml.v3` (which escapes correctly) instead of `text/template` string-concat. Larger change, but eliminates this entire injection class.\n\nOption 2 is preferable long-term. Option 1 is the quick fix.\n\nThe `unsafe_routes` advanced field is already `netip.Parse{Prefix,Addr}`-validated at `enroll.go:226-233` — apply the same validation discipline to the other advanced fields.","aliases":["CVE-2026-47722","GO-2026-5223"],"modified":"2026-06-25T19:56:45.802222792Z","published":"2026-06-08T23:08:15Z","database_specific":{"cwe_ids":["CWE-94"],"severity":"HIGH","github_reviewed":true,"github_reviewed_at":"2026-06-08T23:08:15Z","nvd_published_at":null},"references":[{"type":"WEB","url":"https://github.com/juev/nebula-mesh/security/advisories/GHSA-7hp6-g3pq-3pc3"},{"type":"WEB","url":"https://github.com/forgekeep/nebula-mesh/issues/126"},{"type":"WEB","url":"https://github.com/forgekeep/nebula-mesh/commit/c1506f7344ab375a145a7449b193af3f19bb41ef"},{"type":"PACKAGE","url":"https://github.com/juev/nebula-mesh"}],"affected":[{"package":{"name":"github.com/juev/nebula-mesh","ecosystem":"Go","purl":"pkg:golang/github.com/juev/nebula-mesh"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"0.3.2"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/06/GHSA-7hp6-g3pq-3pc3/GHSA-7hp6-g3pq-3pc3.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N"}]}