Vulnerability · Published Jun 9, 2026 · Assigned by GitHub_M
CVE-2026-46540Nimiq light-blockchain: Light blockchain rebranch issue
Medium 6.5
In plain English
A medium-severity security flaw in core-rs-albatross from nimiq. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 18% of all known vulnerabilities).
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.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| nimiq | core-rs-albatross | < 1.4.0 |
Weakness: CWE-841 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
References
- https://github.com/nimiq/core-rs-albatross/security/advisories/GHSA-m3pg-qc2q-mg8c x_refsource_CONFIRM
- https://github.com/nimiq/core-rs-albatross/pull/3706 x_refsource_MISC
- https://github.com/nimiq/core-rs-albatross/releases/tag/v1.4.0 x_refsource_MISC