CVE-2026-46540 Nimiq light-blockchain: Light blockchain rebranch issue
- Exploited in the wild
- Not known
- Fix
- None listed
What is CVE-2026-46540?
CVE-2026-46540 is a medium-severity vulnerability in nimiq core-rs-albatross, published on 9 Jun 2026.
Official description
Nimiq is a Rust implementation of the Nimiq Proof-of-Stake protocol based on the Albatross consensus algorithm. Prior to version 1.4.0, when LightBlockchain::rebranch() adopts a fork chain whose tip is a macro block (checkpoint or election), it only updates self.head but fails to update self.macro_head, self.election_head, self.current_validators, or store the election header in the chain_store. This is in direct contrast with the full Blockchain::rebranch() at blockchain/src/blockchain/push.rs:504-518, which correctly updates all macro/election state when the new head is a macro block. After a rebranch to a macro block, the stale macro_head causes subsequent macro blocks pushed via push() to be verified against the wrong predecessor via verify_macro_successor(&this.macro_head). If the rebranch target was an election block, the stale current_validators causes every subsequent block to fail verify_validators(), completely stalling the light client's chain progression. This issue has been patched in version 1.4.0.
Weakness: CWE-841
Which versions are affected by CVE-2026-46540?
How do I fix CVE-2026-46540?
No fix has been published for CVE-2026-46540 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-46540 being exploited?
There is no known exploitation of CVE-2026-46540 in the wild and no public exploit code.
Sources
Also known as GHSA-m3pg-qc2q-mg8c.