pgjdbc, the PostgreSQL JDBC Driver, versions 42.7.4 through 42.7.13 pads a value that is shorter than its declared length with bytes left in its send buffer instead of zeros, and the server stores those bytes as part of the value. The bytes are messages the driver sent earlier on the same connection: SQL text and parameter values of recent statements, which on a pooled connection can come from other requests. Each padded value can carry up to 8192 bytes of this traffic, or 16320 bytes on a connection with GSS encryption. The padding happens when an application declares a length larger than the data it supplies, through PreparedStatement.setObject with a ByteStreamWriter, CopyIn.writeToCopy, PGCopyOutputStream.write, LargeObject.write, or Blob.setBytes. The driver accepts these calls…