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nimiq-blockchain: Validity store off by one error

High severity GitHub Reviewed Published Aug 11, 2026 in nimiq/core-rs-albatross • Updated Aug 12, 2026

Package

cargo nimiq-blockchain (Rust)

Affected versions

<= 1.5.0

Patched versions

1.5.1

Description

Impact

The validity store treats a transaction with stored block_number = X as "in window" only when X > last_bn - transaction_validity_window_blocks (strict inequality). However the protocol's Transaction::is_valid_at accepts a transaction for inclusion in any block in [validity_start_height - blocks_per_batch, validity_start_height + window - 1]. By choosing validity_start_height = X + blocks_per_batch (the largest value still compatible with first inclusion at block X), an attacker can replay the same signed transaction in any block B such that X + window < B < validity_start_height + window, i.e., a contiguous window of blocks_per_batch - 1 blocks (59 on MainNet, ~10 minutes) during which the replay-protection check fails to flag it. The same transaction is then executed twice: the sender is debited twice, the recipient credited twice.

Patches

nimiq/core-rs-albatross#3772

Workarounds

No known workarounds

References

@viquezclaudio viquezclaudio published to nimiq/core-rs-albatross Aug 11, 2026
Published to the GitHub Advisory Database Aug 12, 2026
Reviewed Aug 12, 2026
Last updated Aug 12, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

EPSS score

Weaknesses

Off-by-one Error

A product calculates or uses an incorrect maximum or minimum value that is 1 more, or 1 less, than the correct value. Learn more on MITRE.

Authentication Bypass by Capture-replay

A capture-replay flaw exists when the design of the product makes it possible for a malicious user to sniff network traffic and bypass authentication by replaying it to the server in question to the same effect as the original message (or with minor changes). Learn more on MITRE.

CVE ID

CVE-2026-46369

GHSA ID

GHSA-3763-qp59-59vf

Source code

Credits

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