Babelfish for PostgreSQL TDS Prelogin Heap Overflow (CVE-2026-119923)

CVE-2026-119923 is a heap-based buffer overflow in the part of Babelfish for PostgreSQL that parses the first message of a TDS connection, the prelogin packet. Babelfish lets Amazon Aurora PostgreSQL, and self-managed PostgreSQL, understand the TDS wire protocol that SQL Server clients speak. That lets applications built for SQL Server connect without changing drivers.

What NVD and AWS Say About CVE-2026-119923

The NVD record says a specially crafted, malformed TDS prelogin packet sent to the TDS port might allow remote attackers to execute arbitrary OS commands as the database process user. AWS's own security bulletin, 2026-166-AWS, describes the same issue more narrowly, as a memory-safety issue in the TDS connection-handshake handling. AWS says that could allow a remote, unauthenticated actor to affect the confidentiality, integrity and availability of the database process.

The NVD record adds that it consolidates a related null-pointer-dereference finding in the same prelogin parser. Neither the record nor AWS's bulletin names the exact malformed field that triggers either issue, and we leave that detail out.

AWS's bulletin also names a related flaw, CVE-2026-119924, in the same document. AWS describes that one as a separate memory-safety issue in TDS remote-procedure-call request handling. AWS says it could let a remote, authenticated actor read adjacent process memory or cause a denial of service. This page covers only CVE-2026-119923.

NVD and AWS's bulletin both list the same five version ranges of the Babelfish for PostgreSQL extension as affected. Amazon Aurora PostgreSQL with Babelfish enabled is affected across a wide range of engine versions, each tied to one of these extension versions.

AWS's bulletin lists the exact Aurora PostgreSQL engine version that includes each fixed Babelfish version. The table below repeats that list in full.

AWS's bulletin says customers should upgrade their cluster to one of these versions or later and apply any pending maintenance, so the cluster is on the latest patch. Restricting network access to the TDS port, default 1433, is listed as a workaround until that upgrade runs.