Vulnerability details

Network UPS Tools is a collection of programs which provide a common interface for monitoring and administering UPS, PDU and SCD hardware. From 2.8.3 to 2.8.5, upsmon in clients/upsmon.c inserts the server-supplied ups.alarm value into shell commands executed by notify(), async_notify(), and wall(). When a monitored device reports an ALARM state and an operator has configured NOTIFYCMD with EXEC in NOTIFYFLAG ALARM, shell metacharacters in the alarm text are evaluated on POSIX or Windows and can execute arbitrary operating-system commands as the upsmon account, which is commonly root. An attacker can control the value through a malicious or compromised upsd, a man-in-the-middle on a plaintext upsd to upsmon connection, or a compromised UPS device whose driver supplies the alarm upstream of upsd; TLS between upsd and upsmon does not mitigate the compromised-device path. This vulnerability is fixed in 2.8.6.

• https://github.com/networkupstools/nut/security/advisories/GHSA-mjgp-j4gm-6qg5 x_refsource_CONFIRM
• https://github.com/networkupstools/nut/pull/3499 x_refsource_MISC
• https://github.com/networkupstools/nut/commit/98e073d4cc31f9c73e2fa0c2677540487d902fe7 x_refsource_MISC
• https://github.com/networkupstools/nut/commit/dffba911504866695be698bb5ec49eac40d0f66a x_refsource_MISC
• https://github.com/networkupstools/nut/commit/ecf98e7542e4ae2b62b211622ee26989274b2220 x_refsource_MISC
• http://www.openwall.com/lists/oss-security/2026/07/01/10