CVE-2026-34068
MEDIUM6.8EPSS 0.01%nimiq-transaction: UpdateValidator transactions allows voting key change without proof-of-knowledge
Description
### Impact The staking contract accepts `UpdateValidator` transactions that set `new_voting_key=Some(...)` while omitting `new_proof_of_knowledge`. this skips the proof-of-knowledge requirement that is needed to prevent BLS rogue-key attacks when public keys are aggregated. Because tendermint macro block justification verification aggregates validator voting keys and verifies a single aggregated BLS signature against that aggregate public key, a rogue-key voting key in the validator set can allow an attacker to forge a quorum-looking justification while only producing a single signature. While the impact is critical, the exploitability is low: The voting keys are fixed for the epoch, so the attacker would need to know the next epoch validator set (chosen through VRF), which is unlikely. ### Patches [The patch for this vulnerability](https://github.com/nimiq/core-rs-albatross/commit/e7f0ab7d2115e17d6e5548ddc60f10df1a5d645f) is included as part of [v1.3.0](https://github.com/nimiq/core-rs-albatross/releases/tag/v1.3.0). ### Workarounds No known workarounds.
Affected packages (1)
- crates.io/nimiq-transactionfrom 0, <= 0.2.0
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | MEDIUM6.8 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N |
References (6)
- ADVISORYhttps://nvd.nist.gov/vuln/detail/CVE-2026-34068
- PATCHhttps://github.com/nimiq/core-rs-albatross
- WEBhttps://github.com/nimiq/core-rs-albatross/commit/e7f0ab7d2115e17d6e5548ddc60f10df1a5d645f
- WEBhttps://github.com/nimiq/core-rs-albatross/pull/3654
- WEBhttps://github.com/nimiq/core-rs-albatross/releases/tag/v1.3.0
- WEBhttps://github.com/nimiq/core-rs-albatross/security/advisories/GHSA-pf4j-pf3w-95f9