CVE-2019-11841

Ein entfernter, anonymer, authentisierter oder lokaler Angreifer kann mehrere Schwachstellen in IBM DB2 ausnutzen, um Dateien zu manipulieren, Sicherheitsmaßnahmen zu umgehen, vertrauliche Informationen offenzulegen, einen Denial-of-Service-Zustand auszulösen, willkürlichen Code mit erhöhten Rechten auszuführen, Informationen falsch darzustellen und beliebigen Code auszuführen.

A message-forgery issue was discovered in `crypto/openpgp/clearsign/clearsign.go` in supplementary Go cryptography libraries 2019-03-25. According to the OpenPGP Message Format specification in RFC 4880 chapter 7, a cleartext signed message can contain one or more optional "Hash" Armor Headers. The "Hash" Armor Header specifies the message digest algorithm(s) used for the signature. However, the Go clearsign package ignores the value of this header, which allows an attacker to spoof it. Consequently, an attacker can lead a victim to believe the signature was generated using a different message digest algorithm than what was actually used. Moreover, since the library skips Armor Header parsing in general, an attacker can not only embed arbitrary Armor Headers, but also prepend arbitrary text to cleartext messages without invalidating the signatures.

The clearsign package accepts some malformed messages, making it possible for an attacker to trick a human user (but not a Go program) into thinking unverified text is part of the message. With fix, messages with malformed headers in the SIGNED MESSAGE section are rejected.