{"id":"GHSA-v2jf-442r-6mjh","summary":"nebula-mesh: Signed-poll nonce LRU is in-memory and bounded; replay survives restart + eviction","details":"`internal/api/pop/nonce.go:25,40,86` + `internal/api/server.go:38` — the signed-poll nonce cache is an in-process LRU sized at 65,536 entries. `internal/api/updates.go:31` sets `pollClockSkew = 5 * time.Minute` as the replay window.\n\n## Affected\nAll released versions through v0.3.0 that have shipped the ADR 0004 signed-poll path. (If this is gated behind a feature flag, on a side branch, or not yet on a release tag, please flag — this advisory may not apply to the released artifact yet.)\n\n## Threat model\nA captured signed-poll request can be replayed:\n\n1. **After any process restart** — the in-memory LRU is wiped, so the original nonce becomes \"unseen\" again. Replay succeeds if the original timestamp is still within the 5-minute skew.\n2. **After forced eviction** — an attacker with control of any single host can flood \u003e65,536 nonces under their own host_id, driving the global LRU to evict the victim's recorded nonce. Replay then succeeds.\n\nImpact is bounded: a replayed poll fetches the `/api/v1/agent/updates` body. That body can include a freshly-minted enrollment token if a rekey is pending (`updates.go:249-260`) — at which point the attacker holds a single-use token they can redeem under their own keypair.\n\n## Suggested fix\nTwo options, either acceptable:\n\n1. Persist nonces in SQLite keyed by `(host_id, nonce)` with `ON CONFLICT DO NOTHING`, retained for the timestamp-skew window. Adds one transactional INSERT per poll; bounded by the skew window (~5 min worth of rows server-wide).\n2. Per-host cap on the LRU instead of a global 65k cap, so one host cannot evict another's records. Combined with shorter skew (≤30s) to bound the post-restart replay window.\n\nOption 1 is more robust; option 2 is lower-implementation-effort.","aliases":["GO-2026-5815"],"modified":"2026-07-07T16:11:36.907200554Z","published":"2026-06-26T21:01:09Z","database_specific":{"severity":"LOW","github_reviewed":true,"github_reviewed_at":"2026-06-26T21:01:09Z","nvd_published_at":null,"cwe_ids":["CWE-294"]},"references":[{"type":"WEB","url":"https://github.com/juev/nebula-mesh/security/advisories/GHSA-v2jf-442r-6mjh"},{"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":"0.3.4"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/06/GHSA-v2jf-442r-6mjh/GHSA-v2jf-442r-6mjh.json","last_known_affected_version_range":"\u003c= 0.3.3"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U"}]}