CVE-2026-103436 Details
Description
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.
A vulnerability in the apcupsd UPS control software, specifically in the CGI component, has been identified. This issue, present in versions through 3.14.14, involves a stack-based buffer overflow and the disclosure of uninitialized memory. The vulnerability arises in the 'getupsvar()' function within 'src/cgi/upsfetch.c', which is utilized by several CGI scripts including 'upsstats.cgi', 'multimon.cgi', and 'upsfstats.cgi'. When these scripts fetch UPS status from a networked apcupsd server, the 'getupsvar()' function can be tricked into overflowing a buffer with unbounded data from the server, while also leaking uninitialized stack memory back to the user via the HTTP response.
The vulnerability can be fixed by applying the same bounds-checking logic that was previously corrected in the daemon-side version of 'getupsvar()' to the CGI version. This involves limiting the data copied into buffers to prevent overflow and ensuring that all memory is properly initialized before being used.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed Sep 30, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://bugzilla.redhat.com/show_bug.cgi?id=2493140 | [email protected] | Issue TrackingTechnical DescriptionVendor |
| https://github.com/therealbstern/apcupsd/blob/224d19d5faa508d04267f6135fe53d50800550de/src/cgi/upsfetch.c#L240 | [email protected] | Source CodeVendor |
| https://sourceforge.net/projects/apcupsd/ | [email protected] | ProductVendor |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-457 | Use of Uninitialized Variable | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| apcupsd | 3.14.14 (semver) |
CPE
Remediation
| |
| Fedora | All versions |
CPE
Remediation
| |
Change History
1 change record found show changes
| Date | Action | Recorded By |
|---|---|---|
| Sep 30, 2026 | New CVE Received | [email protected] |