CVE-2026-58262 in klever-go
Summary
by MITRE • 08/08/2026
Klever-Go is the Go implementation of the Klever blockchain protocol. Prior to 1.7.20, header signature verification counts the unused padding bits of the PubKeysBitmap toward the two-thirds validator quorum. These padding bits do not correspond to any validator and are ignored by the actual BLS aggregate-signature check, so a malicious or compromised block producer can set them to reach the required quorum while gathering fewer genuine validator signatures than the protocol demands. As a result, nodes that import or intercept the header accept it as correctly signed without a real two-thirds quorum, weakening consensus safety and undermining finality. This issue is fixed in version 1.7.20.
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Analysis
by VulDB Data Team • 08/08/2026
The vulnerability in Klever-Go represents a critical consensus flaw that undermines the fundamental security guarantees of the blockchain protocol. This issue affects versions prior to 1.7.20 where the header signature verification process incorrectly includes unused padding bits from the PubKeysBitmap when calculating validator quorum requirements. The flaw stems from improper handling of bit-level data structures within the BLS signature verification mechanism, creating a scenario where malicious actors can manipulate consensus outcomes through artificial padding bits that have no legitimate validator association.
The technical implementation defect lies in how the system counts validator signatures during header verification, specifically when processing the PubKeysBitmap structure which contains both valid validator public keys and unused padding bits. During quorum calculation, the protocol incorrectly treats these padding bits as active validators, allowing a block producer to artificially inflate their signature count beyond what is actually present in the network. This miscounting occurs because while the actual BLS aggregate-signature verification correctly ignores padding bits, the quorum threshold calculation does not distinguish between legitimate validator signatures and meaningless padding data.
The operational impact of this vulnerability creates a significant risk to consensus safety and transaction finality within the Klever blockchain network. Nodes accepting blocks that contain manipulated header signatures will incorrectly believe they have achieved the required two-thirds validator quorum, even when fewer than the actual number of validators have signed the block. This discrepancy allows malicious actors to produce invalid blocks that appear valid to the network, potentially leading to double-spending attacks, transaction rollback scenarios, and overall network instability. The vulnerability essentially creates a false sense of security around consensus validation while undermining the cryptographic guarantees that ensure blockchain integrity.
This issue aligns with CWE-284 Access Control Bypass and represents a specific implementation flaw in the BLS signature verification protocol as outlined in the ATT&CK framework under privilege escalation techniques. The vulnerability demonstrates poor input validation and incorrect bit manipulation handling, where padding bits that should be ignored during quorum calculations are instead counted toward consensus requirements. The fix implemented in version 1.7.20 addresses this by ensuring that only legitimate validator signatures from the PubKeysBitmap are considered when determining whether the required two-thirds quorum has been achieved, thereby restoring proper cryptographic security guarantees to the blockchain consensus mechanism and preventing unauthorized manipulation of network validation processes.