GHSA-2557-x9mg-76w8: 
vulnerability analysis and mitigation

A medium severity vulnerability (GHSA-2557-x9mg-76w8) was identified in the Cosmos SDK affecting versions <= 0.50.3 and <= 0.47.8. The issue, discovered on January 16, 2024, involves the default PrepareProposalHandler when used with the default SenderNonceMempool, which could potentially allow invalid blocks to be proposed when a single sender includes multiple transactions with non-sequential sequence numbers under certain conditions (GitHub Advisory).

The vulnerability has been assigned a CVSS score of 5.3 (Moderate) with the following characteristics: Network attack vector, Low attack complexity, No privileges required, No user interaction needed, Unchanged scope, and Low availability impact. The technical vector string is CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L. The issue is classified under CWE-1285 (GitHub Advisory).

The vulnerability can lead to a reduction in block production for affected networks. When exploited, it affects the network's ability to process transactions efficiently, potentially resulting in a Denial of Service condition (GitHub Advisory).

The vulnerability can be triggered when a single sender includes multiple transactions with non-sequential sequence numbers under specific conditions. The attack vector is network-based with low complexity and requires no special privileges or user interaction (GitHub Advisory).

Chain developers using affected versions of the Cosmos SDK are advised to update to the patched versions: v0.50.4 for the v0.50.x line or v0.47.9 for the v0.47.x line. Network operators should ensure that 2/3 of the validator power upgrades to the patched versions (SDK Release, GitHub Advisory).