MariaDB Connector/J is used to connect applications developed in Java to MariaDB and MySQL databases. From 3.0.0 until 3.3.7, 3.4.5, and 3.5.10, the ReadableByteBuf.readLength() and ReadableByteBuf.readIntLengthEncodedNotNull() methods narrowed the protocol's unsigned 8-byte length-encoded integer to a Java int without checking that the value fit a non-negative integer. Values above Integer.MAX_VALUE could wrap to a negative or unrelated length that downstream allocation and read paths used. A malicious or compromised server, or a machine-in-the-middle attacker, could trigger NegativeArraySizeException, out-of-bounds failures, or oversized allocation behavior in client connection handling. This issue is fixed in versions 3.3.7, 3.4.5, and 3.5.10.

Affected: Maven: org.mariadb.jdbc:mariadb-java-client

## Summary

MariaDB Connector/J narrowed 8-byte length-encoded integers received from the server to `int` without validation. A rogue or MitM server can send a value above `Integer.MAX_VALUE` whose truncation becomes a negative or arbitrary length.

## Details

The protocol encodes lengths as length-encoded integers, whose 8-byte form the decoder (`readLength()` and `readIntLengthEncodedNotNull()`) returned as `(int) readLong()`. A value above `Integer.MAX_VALUE` therefore wrapped to a negative or unrelated `int`, used afterwards as a length to size allocations or reads, which ended in `NegativeArraySizeException`, out-of-bounds exceptions or oversized allocations.

The fix rejects any length-encoded value that does not fit a non-negative `int` with an explicit error.

## Impact

Availability only: a malicious or compromised server, or a MitM, can crash the client's connection handling with unchecked exceptions or drive oversized allocations. Exploitation requires control of the server side of the connection; no authentication bypass, confidentiality or integrity impact.

## Credit

Reported by fg0x0

Affected: Ubuntu:18.04:LTS: mariadb-connector-java, Ubuntu:20.04:LTS: mariadb-connector-java, Ubuntu:22.04:LTS: mariadb-connector-java, Ubuntu:24.04:LTS: mariadb-connector-java, Ubuntu:26.10: mariadb-connector-java, Ubuntu:26.04:LTS: mariadb-connector-java

MariaDB Connector/J is used to connect applications developed in Java to MariaDB and MySQL databases. From 3.0.0 until 3.3.7, 3.4.5, and 3.5.10, the ReadableByteBuf.readLength() and ReadableByteBuf.readIntLengthEncodedNotNull() methods narrowed the protocol's unsigned 8-byte length-encoded integer to a Java int without checking that the value fit a non-negative integer. Values above Integer.MAX_VALUE could wrap to a negative or unrelated length that downstream allocation and read paths used. A malicious or compromised server, or a machine-in-the-middle attacker, could trigger NegativeArraySizeException, out-of-bounds failures, or oversized allocation behavior in client connection handling. This issue is fixed in versions 3.3.7, 3.4.5, and 3.5.10.