{"schema":"threatline.record/2","record":{"id":"CVE-2026-82407","aliases":["GHSA-9wh6-9hq7-9688","GO-2026-6586"],"summary":"Klever-Go: Validator registration accepts an unvalidated BLS public key → consensus liveness DoS","details":"**Location:** `core/kapp/validators/validators.go:201` (`Register`), (`genesis/checking/nodesSetupChecker.go:73`). `core/consensus/slot/bls/subslotStartSlot.go:165` `core/consensus/.../headerSignatureVerify.go:123` (`Create(...)`).\n\n### Description\n\nKlever uses a BDN (Boneh-Drijvers-Neven) BLS multi-signature over BLS12-381 to finalize blocks (`crypto/signing/mcl/multisig/bls.go`, herumi/bls-go-binary). The library is initialized with only `bls.Init(bls.BLS12_381)` and no order-verification flags, so `Deserialize` does not enforce prime-order-subgroup membership  subgroup safety relies on explicit `IsValidOrder()` calls in the wrappers.\n\nRuntime validator registration (`validators.Register`) stores the submitted 96-byte `BLSPublicKey` via `SetBLSPublicKey` with **no curve check, no subgroup check, and no proof-of-possession** (`CreateValidatorContract` carries the key but no signature proving key ownership; grep confirms no `proofOfPossession`/`VerifyProof`/`BLSSignature` verification anywhere in `core/kapp/validators/`). `CheckPublicKeyValid` — which does `IsValid && IsValidOrder && !IsZero` — runs only at genesis, not on runtime registration/update.\n\n### POC\n\nAttack: \n(1) stake the minimum to register a validator, submitting a 96-byte `BLSPublicKey` that is not a valid G2 point (arbitrary bytes). Registration succeeds. \n(2) Once the validator is eligible and selected into a consensus group, every in-group node  including the honest leader (`group[0]`)  calls `MultiSigner().Reset(groupPubKeys, selfIndex)` at slot start, which deserializes all group keys via `PublicKeyFromByteArray` → herumi `Deserialize` **deterministically fails** on the malformed key → `SetSlotCanceled(true)`. The verify side (`Create(consensusPubKeys)`) fails identically. No block is produced for that round. \n\n\n\n### Impact\n\nEvery consensus round whose group contains the malformed-key validator is a missed slot. One eligible bad-key validator poisons roughly a `groupSize / eligibleSet` fraction of rounds → sustained liveness degradation. **Where the consensus group equals the eligible set (small or early-stage networks), this is a full chain halt.** Cost is the minimum validator stake, permissionless, and repeatable; no fork flag gates the missing validation. \n\nRated **High** (Byzantine liveness; Critical on small validator sets). The severity scales down to a fractional missed-slot / throughput-degradation attack on a large validator set where the bad validator is only occasionally in the active group.\n\n### Recommendation\n\nEnforce `CheckPublicKeyValid` (curve + prime-order subgroup + non-zero) on the submitted BLS key at runtime validator registration and config-update, and ideally require a proof-of-possession (a BLS signature over the validator's own key/identity) at registration to prove key ownership and well-formedness. Gate the stricter validation behind an epoch fork flag for reprocessing consistency.","categories":["Libraries & packages"],"product":"github.com/klever-io/klever-go","vendor":"klever-io","ecosystem":"go","affected_ranges":[{"source":"GitHub Advisory Database","source_url":"https://github.com/advisories/GHSA-9wh6-9hq7-9688","source_modified_at":"2026-09-23T21:24:09Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"ecosystem":"go","name":"github.com/klever-io/klever-go"},"range":"<= 1.7.19"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-82407","source_modified_at":"2026-09-23T19:42:17.556Z","fetched_at":"2026-10-23T18:45:31.882637Z","product":"klever-go","vendor":"klever-io","versions":[{"version":"< 1.7.20","status":"affected"}],"defaultStatus":null},{"source":"OSV","source_url":"https://osv.dev/vulnerability/GHSA-9wh6-9hq7-9688","source_modified_at":"2026-10-01T20:56:13.319048406Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"github.com/klever-io/klever-go","ecosystem":"Go","purl":"pkg:golang/github.com/klever-io/klever-go"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"1.7.20"}]}],"versions":[]}],"fixed_versions":[{"source":"GitHub Advisory Database","source_url":"https://github.com/advisories/GHSA-9wh6-9hq7-9688","source_modified_at":"2026-09-23T21:24:09Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"ecosystem":"go","name":"github.com/klever-io/klever-go"},"version":"1.7.20"},{"source":"OSV","source_url":"https://osv.dev/vulnerability/GHSA-9wh6-9hq7-9688","source_modified_at":"2026-10-01T20:56:13.319048406Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"github.com/klever-io/klever-go","ecosystem":"Go","purl":"pkg:golang/github.com/klever-io/klever-go"},"version":"1.7.20"}],"cvss":7,"severity":"High","kev":{"listed":false},"epss":{"probability":0.00434,"percentile":0.36634,"score_date":"2026-10-23"},"published_at":"2026-09-23T19:17:59.006Z","modified_at":"2026-10-01T20:56:13.319048406Z","provenance":[{"source":"GitHub Advisory Database","url":"https://github.com/advisories/GHSA-9wh6-9hq7-9688","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-09-23T21:24:09Z"},{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-82407","fetched_at":"2026-10-23T18:45:31.882637Z","source_modified_at":"2026-09-23T19:42:17.556Z"},{"source":"OSV","url":"https://osv.dev/vulnerability/GHSA-9wh6-9hq7-9688","fetched_at":"2026-10-23T18:45:31.882637Z","source_modified_at":"2026-10-01T20:56:13.319048406Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-82407","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23"}],"sources":["GitHub Advisory Database","CVE List","OSV","EPSS"],"references":[{"source":"CVE List","url":"https://github.com/klever-io/klever-go/security/advisories/GHSA-9wh6-9hq7-9688","tags":["exploit"]},{"source":"CVE List","url":"https://github.com/klever-io/klever-go/commit/11606a90ccc289f93d0175994733229b332d9cff","tags":["x_refsource_MISC"]},{"source":"CVE List","url":"https://github.com/klever-io/klever-go/commit/642da967893884d635986fed3c43bdc679cbfe8f","tags":["x_refsource_MISC"]},{"source":"CVE List","url":"https://github.com/klever-io/klever-go/releases/tag/v1.7.20","tags":["x_refsource_MISC"]},{"url":"https://github.com/advisories/GHSA-9wh6-9hq7-9688","source":"GitHub Advisory Database"}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"cve_state":"PUBLISHED","ssvc":{"exploitation":"poc","automatable":"no","technical_impact":"partial","assessed_at":"2026-09-23T19:41:57.322149Z"},"classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":"ecosystem","confidence":"heuristic","reviewed":false},"change_timestamp":"2026-10-01T20:56:13.319048406Z","content_hash":"a7712fa9f8ccd0c51dee7b3905ec1b16e3fa263580354089fea86ae9d6c93528"}}