Executive brief
Nimiq Albatross is a blockchain protocol implementation used for processing cryptocurrency transactions. A vulnerability in the validator component allows an unauthenticated attacker to remotely crash the server by sending a specially crafted message. This results in a denial-of-service, potentially disrupting the consensus network and halting transaction processing.
Technical details
An off-by-one error exists in the `ProposalSender::send` function within the `nimiq-validator` crate. The code uses a `>` operator instead of `>=` when performing a bounds check on the `signer` field of a Tendermint proposal message against the total number of validators. If an untrusted peer sends a message where the signer index is exactly equal to the number of validators, the check passes and triggers a call to `validators.get_validator_by_slot_band(signer)`. This results in an out-of-bounds index panic, crashing the process before signature verification occurs. The issue is fixed in version 1.3.0.
Affected products
- Nimiq core-rs-albatross (nimiq-validator) < 1.3.0
Timeline
- 2026-03-27: patched: Fix merged and version 1.3.0 released
- 2026-04-11: advisory: GitHub Security Advisory published
- 2026-04-13: disclosed: CVE-2026-32605 published