An issue was discovered in Rsyslog v8.1908.0. contrib/pmcisconames/pmcisconames.c has a heap overflow in the parser for Cisco log messages. The parser tries to locate a log message delimiter (in this case, a space or a colon), but fails to account for strings that do not satisfy this constraint. If the string does not match, then the variable lenMsg will reach the value zero and will skip the sanity check that detects invalid log messages. The message will then be considered valid, and the parser will eat up the nonexistent colon delimiter. In doing so, it will decrement lenMsg, a signed integer, whose value was zero and now becomes minus one. The following step in the parser is to shift left the contents of the message. To do this, it will call memmove with the right pointers to the target and destination strings, but the lenMsg will now be interpreted as a huge value, causing a heap overflow. Reference: https://github.com/rsyslog/rsyslog/pull/3883
Created rsyslog tracking bugs for this issue: Affects: fedora-all [bug 1766701]
Upstream commit: https://github.com/rsyslog/rsyslog/pull/3883/commits/abc0960a7561e18944a0e08d48f4eb570ea7435a A flaw in the way rsyslog parses Cisco log messages. Crafted messages could result in crash or even code execution, however since log messages are normally generated by the system and privs are required to generate specially-crafted messages, it is more likely to result in rsyslog crash rather than code execution.
This issue has been addressed in the following products: Red Hat Enterprise Linux 7 Via RHSA-2020:1000 https://access.redhat.com/errata/RHSA-2020:1000
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s): https://access.redhat.com/security/cve/cve-2019-17042
This issue has been addressed in the following products: Red Hat Enterprise Linux 8 Via RHSA-2020:1702 https://access.redhat.com/errata/RHSA-2020:1702