PostgreSQL Integer Underflow (Wrap or Wraparound) Vulnerability - CVE-2026-16241

Integer underflow in PostgreSQL ECPG allows a database server administrator to achieve temporary denial of service against the ECPG client via sending a bytea value lacking the mandatory prefix. The client overwrites a huge memory region with bytes outside attacker knowledge or control. This typically yields a simple SIGSEGV but rare cases might achieve client-specific integrity impact via the write. Versions before PostgreSQL 18.5 17.11 16.15 15.19 and 14.24 are affected.