CVE-2026-19654

Rsyslog is a fast system for log processing. From versions 1.15.0 to 8.2610.0, rsyslog's omfile dynaFile facility intentionally allows templates to generate flexible output paths. A deployment becomes unsafe when a dynaFile template uses a value influenced by untrusted input as a path component without explicit secure-path handling, allowing the rendered path to escape the intended log directory. This is not limited to the RFC5424 HOSTNAME field. At time of publication, there are no publicly available patches.

In Rsyslog from 7.5.4 until 8.2606.0, the optional mmpstrucdata plugin's parseSD_PARAM function 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 parameter larger than the buffer, causing an attacker-controlled stack overwrite. This is fixed in version 8.2606.0.

In Rsyslog from 8.2110.0 until 8.2604.0, the optional imhttp module's parse_auth_header function allocates a zero-byte heap buffer with calloc(0, len) when an HTTP Basic Authorization value exceeds its fixed work buffer, then passes that pointer to apr_base64_decode. An unauthenticated remote attacker can send an oversized encoded credential to an imhttp endpoint configured for Basic Authentication, causing decoded data to overwrite adjacent heap memory before credential validation. This is fixed in version 8.2604.0.

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.