# CVE-2026-54161: upsmon: remote OS command injection (RCE) via attacker-controlled ups.alarm in NOTIFYCMD execution

Status: published. Published: 2026-11-03. Updated: 2026-11-03.

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.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- networkupstools / nut: >= 2.8.3, <= 2.8.5 (affected). Source: CNA: GitHub_M

## Severity and prioritization

- CVSS 3.1: 8.1 (high); CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H; source: CNA: GitHub_M

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-78

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/networkupstools/nut/security/advisories/GHSA-mjgp-j4gm-6qg5 (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/networkupstools/nut/pull/3499 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/networkupstools/nut/commit/98e073d4cc31f9c73e2fa0c2677540487d902fe7 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/networkupstools/nut/commit/dffba911504866695be698bb5ec49eac40d0f66a (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/networkupstools/nut/commit/ecf98e7542e4ae2b62b211622ee26989274b2220 (CNA: GitHub_M; x_refsource_MISC)

- http://www.openwall.com/lists/oss-security/2026/07/01/10 (ADP: CVE)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-54161; retrieved 2026-11-03; source updated 2026-11-03

Revision: 6792b6e1e543b4712f4f02ada24223f642b66d1d9539e892b35960723f0a1873

Canonical: https://y2.dev/cve/CVE-2026-54161

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