Issues fixed in this release (since 5.7.2):

• fix an mda buffer truncation bug which allows a user to create forward files that pass session checks but fail delivery later down the chain, within the user mda;
• fix remote buffer overflow in unprivileged pony process;
• reworked offline enqueue to better protect against hardlink attacks.

Several vulnerabilities have been fixed in OpenSMTPD 5.7.2:

• an oversight in the portable version of fgetln() that allows attackers to read and write out-of-bounds memory;

• multiple denial-of-service vulnerabilities that allow local users to kill or hang OpenSMTPD;

• a stack-based buffer overflow that allows local users to crash OpenSMTPD, or execute arbitrary code as the non-chrooted _smtpd user;

• a hardlink attack (or race-conditioned symlink attack) that allows local users to unset the chflags() of arbitrary files;

• a hardlink attack that allows local users to read the first line of arbitrary files (for example, root's hash from /etc/master.passwd);

• a denial-of-service vulnerability that allows remote attackers to fill OpenSMTPD's queue or mailbox hard-disk partition;

• an out-of-bounds memory read that allows remote attackers to crash OpenSMTPD, or leak information and defeat the ASLR protection;

• a use-after-free vulnerability that allows remote attackers to crash OpenSMTPD, or execute arbitrary code as the non-chrooted _smtpd user;

Further details can be found in Qualys' audit report: http://seclists.org/oss-sec/2015/q4/17

MITRE has assigned one CVE for the use-after-free vulnerability; additional CVEs may be assigned: http://seclists.org/oss-sec/2015/q4/23

External References:

https://www.opensmtpd.org/announces/release-5.7.2.txt http://seclists.org/oss-sec/2015/q4/17