CVE-2026-61548

Rsyslog is a rocket-fast system for log processing. From 7.5.4 until 8.2606.0, the optional mmpstrucdata plugin's parseSD_PARAM function in plugins/mmpstrucdata/mmpstrucdata.c stores RFC5424 parameter values in a fixed pVal[32 * 1024] stack buffer and calls parsePARAM_VALUE without supplying the destination size. A remote unauthenticated attacker whose crafted RFC5424 message reaches an action using mmpstrucdata can provide a structured-data parameter larger than that buffer when MaxMessageSize permits it, causing an attacker-controlled stack overwrite. Deployments that do not install and use the plugin, or whose effective message-size limit remains below the required threshold, are not affected by this issue. The demonstrated impact is a crash and interruption of log collection; code execution is not demonstrated. This issue is fixed in version 8.2606.0.

• https://github.com/rsyslog/rsyslog/commit/bcda60a3692efdf0c8e44102528f5a0ebe0dec6d
• https://github.com/rsyslog/rsyslog/pull/6991
• https://github.com/rsyslog/rsyslog/releases/tag/v8.2606.0
• https://github.com/rsyslog/rsyslog/security/advisories/GHSA-8qmr-c66f-g368
• http://www.openwall.com/lists/oss-security/2026/07/20/1