MITRE description:

PostgreSQL 8.1.x before 8.1.4, 8.0.x before 8.0.8, 7.4.x before 7.4.13, 7.3.x before 7.3.15, and earlier versions allows context-dependent attackers to bypass SQL injection protection methods in applications that use multibyte encodings that allow the "\" (backslash) byte 0x5c to be the trailing byte of a multibyte character, such as SJIS, BIG5, GBK, GB18030, and UHC, which cannot be handled correctly by a client that does not understand multibyte encodings, aka a second variant of "Encoding-Based SQL Injection." NOTE: it could be argued that this is a class of issue related to interaction errors between the client and PostgreSQL, but a CVE has been assigned since PostgreSQL is treating this as a preventative measure against this class of problem.