The binary delta decoder in Mercurial before 3.7.3 allows remote attackers to execute arbitrary code via a (1) clone, (2) push, or (3) pull command, related to (a) a list sizing rounding error and (b) short records.
The _validaterepo function in sshpeer in Mercurial before 3.2.4 allows remote attackers to execute arbitrary commands via a crafted repository name in a clone command.