CVE-2026-107349

PgBouncer 1.6.x before 1.6.1, when configured with auth_user, allows remote attackers to gain login access as auth_user via an unknown username.

PgBouncer before 1.5.5 allows remote attackers to cause a denial of service (NULL pointer dereference and crash) by sending a password packet before a startup packet.

Improper authentication in PgBouncer 1.17.0 through 1.26.0 allows a remote attacker who knows the password of a user listed in auth_file to log in as any other user that authenticates using SCRAM, including PgBouncer admin users and backend superusers. A second StartupMessage sent during SCRAM authentication against a non-existent database is not rejected and switches the user being logged in as, while the SCRAM exchange is still verified against the keys of the first user.

Integer overflow in the message buffer growth logic (mbuf_make_room) in PgBouncer 1.21.0 through 1.26.0 allows a remote attacker to cause a denial of service when max_packet_size is configured above 2147483648. A packet header declaring a length above 2^31 makes the buffer size computation overflow, leaving the growth loop unable to terminate, saturating a CPU core and stalling every pooled connection until the process is restarted. Since 1.23.0 the overflow is reachable before authentication with a five-byte packet header.

PgBouncer through 1.25.2 lacks an upper bound on the key derivation iteration count accepted during SCRAM authentication to a backend server. A malicious or compromised PostgreSQL backend can cause uncontrolled CPU consumption in PgBouncer, and the key derivation cannot be interrupted in frontend builds.

Integer overflow in the packet buffer growth logic in PgBouncer through 1.25.2 allows an unauthenticated remote attacker to cause a denial of service. Sufficiently large input makes the buffer size computation overflow, leaving the growth loop unable to terminate. Because PgBouncer serves all clients from a single process, this saturates a CPU core and stalls every pooled connection until the process is killed. Both unauthenticated and authenticated code paths can reach the overflow.

Missing validation of a mandatory attribute in the SCRAM client-final-message parser in PgBouncer through 1.25.2 allows an unauthenticated remote attacker to crash the process. A malformed message can make the parser report success while leaving a required value unset, which is then dereferenced as a NULL pointer. The crash occurs before any credential is verified, so no valid account is required. Because PgBouncer serves all clients from a single process, this terminates every pooled connection.

PgBouncer before 1.25.2 did not properly authorize the KILL_CLIENT admin command. Any user with access to the admin console could run it, instead of only users in the admin_users list.

In PgBouncer before version 1.25.2, a null pointer dereference could cause a crash if a server sends an error response without the SQLSTATE field.

The SCRAM code in PgBouncer before version 1.25.2 does not correctly check the return value of strlcat() when building the client-final-message. A malicious backend sending a server-final-message with a long nonce can trigger a stack overflow.