Executive brief
Nimiq core-rs-albatross is a Rust implementation of the Nimiq blockchain protocol. A vulnerability allowed a malicious network validator to propose a specially crafted block that bypasses certain security checks. This could lead to a situation where the blockchain network reaches a consensus on a block that it later rejects, potentially causing a denial of service or disrupting the stability of the blockchain.
Technical details
A vulnerability in the Nimiq core-rs-albatross implementation of the Albatross consensus protocol allows an elected validator proposer to submit an election macro block with a malformed 'header.interlink'. The 'verify_macro_block_proposal()' function fails to validate the interlink binding for election blocks, even though it checks other header properties. While the block is accepted during the Tendermint proposal phase, it is subsequently rejected with an 'InvalidInterlink' error during the 'verify_block()' push phase. Because validators have already prevoted and precommitted the malformed header hash, the failure occurs after the block is finalized, leading to a consensus disruption. This issue is fixed in version 1.3.0 by extracting the interlink check into a shared verification path.
Affected products
- Nimiq core-rs-albatross < 1.3.0
Timeline
- 2026-03-27: patched: Fix committed and version 1.3.0 released.
- 2026-04-03: disclosed: Advisory published.