Fetchmail is a remote mail retrieval and forwarding utility.
Neil Hoggarth has discovered that when delivering messages to a message delivery agent by means of the "mda" option, Fetchmail passes a NULL pointer to the ferror() and fflush() functions when refusing a message. Isaac Wilcox has discovered numerous means of plain-text password disclosure due to errors in secure connection establishment.
An attacker could deliver a message via Fetchmail to a message delivery agent configured to refuse the message, and crash the Fetchmail process. SMTP and LMTP delivery modes are not affected by this vulnerability. An attacker could also perform a Man-in-the-Middle attack, and obtain plain-text authentication credentials of users connecting to a Fetchmail process.
There is no known workaround at this time.
All fetchmail users should upgrade to the latest version:
# emerge --sync # emerge --ask --oneshot --verbose ">=net-mail/fetchmail-6.3.6"