CVE-2026-78002

A flaw was found in rsyslog. An unauthenticated remote attacker can trigger a heap buffer overflow in the RainerScript replace() function by sending specially crafted syslog messages. This vulnerability arises from an incorrect buffer size calculation during string replacement, causing memory corruption. Successful exploitation can lead to a denial of service (DoS) for the affected system.

This Important flaw in rsyslog allows an unauthenticated remote attacker to trigger a heap buffer overflow, leading to a denial of service. The vulnerability occurs when processing specially crafted syslog messages containing specific RainerScript replace() function calls. Red Hat Enterprise Linux systems configured to receive remote syslog messages are susceptible to this issue, potentially impacting logging availability.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this vulnerability, restrict network access to the rsyslog service to only trusted hosts. This can be achieved by configuring firewall rules to limit incoming connections to UDP and TCP port 514. Alternatively, if remote syslog reception is not required, disable the imudp and imtcp modules in the /etc/rsyslog.conf configuration file. After modifying the rsyslog configuration or firewall rules, the rsyslog service or firewall service must be restarted for the changes to take effect.