pgjdbc pads a value shorter than its declared length with bytes of earlier statements (rather than zeros)

Overview

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 without an error. An attacker who can make the application store such a value and read it back can collect earlier traffic. Applications whose declared lengths always match their data are not affected. Versions 42.7.3 and earlier pad with zeros.

Affected

• org.postgresql:postgresql >= 42.7.4 <= 42.7.13

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

Workarounds

Make the declared length match the data: ByteStreamWriter.getLength() must equal the number of bytes writeTo() writes, and the (offset, length) passed to the byte-array methods must lie within the array. No connection property turns the behavior off.