RabbitMQ amqp091-go, a Go client for AMQP 0.9.1, improperly checks for exceptional conditions in the readLongstr function before version 1.13.0. When the declared AMQP long string length exceeds 0x7FFFFFFF, readLongstr returns an empty string and nil error instead of ErrSyntax. This leaves the declared field bytes unread, causing readTable to continue parsing from an incorrect offset. A malicious or compromised broker can exploit this by sending an oversized long string in a table field, leading to desynchronization of AMQP parsing and disruption of connection integrity and availability. The vulnerability is addressed in version 1.13.0.

An attacker controlling or compromising the AMQP broker can send an oversized long string to the client, causing the client to misinterpret subsequent data frames. This desynchronization can disrupt the connection's integrity and availability, potentially leading to denial of service or other communication issues. The vulnerability has a high CVSS 4.0 score of 9.5, indicating critical severity with high impact on confidentiality, integrity, and availability.

Upgrade RabbitMQ amqp091-go to version 1.13.0 or later, where this issue is fixed. No other mitigation is indicated or required according to the available information.