rsyslog: Rsyslog is a rocket-fast system for log processing

Rsyslog is a rocket-fast system for log processing. Modules for TCP syslogreception have a potential heap buffer overflow when octet-counted framingis used. This can result in a segfault or some other malfunction. As of ourunderstanding, this vulnerability can not be used for remote codeexecution. But there may still be a slight chance for experts to do that.The bug occurs when the octet count is read. While there is a check for themaximum number of octets, digits are written to a heap buffer even when theoctet count is over the maximum, This can be used to overrun the memorybuffer. However, once the sequence of digits stop, no additional characterscan be added to the buffer. In our opinion, this makes remote exploitsimpossible or at least highly complex. Octet-counted framing is one of twopotential framing modes. It is relatively uncommon, but enabled by defaulton receivers. Modules `imtcp`, `imptcp`, `imgssapi`, and `imhttp` are usedfor regular syslog message reception. It is best practice not to directlyexpose them to the public. When this practice is followed, the risk isconsiderably lower. Module `imdiag` is a diagnostics module primarilyintended for testbench runs. We do not expect it to be present on anyproduction installation. Octet-counted framing is not very common. Usually,it needs to be specifically enabled at senders. If users do not need it,they can turn it off for the most important modules. This will mitigate thevulnerability.

Where it's fixed