libs/comverp.c in Courier MTA before 0.53.2 allows attackers to cause a denial of service (CPU consumption) via unknown vectors involving usernames that contain the "=" (equals) character, which is not properly handled during encoding.

Multiple buffer overflows in (1) iso2022jp.c or (2) shiftjis.c for Courier-IMAP before 3.0.0, Courier before 0.45, and SqWebMail before 4.0.0 may allow remote attackers to execute arbitrary code "when Unicode character is out of BMP range."

SQL injection vulnerability in the PostgreSQL auth module for courier 0.40 and earlier allows remote attackers to execute SQL code via the user name.

Courier sqwebmail before 0.40.0 does not quickly drop privileges after startup in certain cases, which could allow local users to read arbitrary files.

Double Precision Courier e-mail MTA allows remote attackers to cause a denial of service (CPU consumption) via a message with an extremely large or negative value for the year, which causes a tight loop.