Unknown vulnerability in apcupsd before 3.8.6, and 3.10.x before 3.10.5, allows remote attackers to gain root privileges, possibly via format strings in a request to a slave server.

Apcupsd 0.3.915, as used in pfSense through 2.4.4-RELEASE-p3 and other products, has an Arbitrary Command Execution issue in apcupsdstatus.php.

In Adam Kropelin adk0212 APC UPS Daemon through 3.14.14, the default installation of APCUPSD allows a local authenticated, but unprivileged, user to run arbitrary code with elevated privileges by replacing the service executable apcupsd.exe with a malicious executable that will run with SYSTEM privileges at startup. This occurs because of "RW NT AUTHORITY\Authenticated Users" permissions for %SYSTEMDRIVE%\apcupsd\bin\apcupsd.exe.

apcupsd through 3.14.14 has an sscanf stack-based buffer overflow in getupsvar() in src/cgi/upsfetch.c (used by upsstats.cgi, multimon.cgi, and upsfstats.cgi), a related issue to CVE-2026-15544.

Apcupsd 0.3.915, as used in pfSense through 2.4.4-RELEASE-p3 and other products, has an XSS issue in apcupsdstatus.php.

apcupsd through 3.14.14 discloses uninitialized stack memory in getupsvar() in src/cgi/upsfetch.c (used by upsstats.cgi, multimon.cgi, and upsfstats.cgi. On the single-field path, when the matched STATUS line has fewer than three whitespace-separated tokens, sscanf("%s %s %s", answer) performs no assignment but the function returns success, and thus the caller prints the uninitialized destination buffer into the HTTP response.