CVE-2021-47890
Published: 23 January 2026
Summary
CVE-2021-47890 is a high-severity Unquoted Search Path or Element (CWE-428) vulnerability in Logonexpert (inferred from references). Its CVSS base score is 8.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Path Interception by Unquoted Path (T1574.009); ranked at the 2.1th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified are NIST 800-53 CM-6 (Configuration Settings) and RA-5 (Vulnerability Monitoring and Scanning).
Deeper analysis
CVE-2021-47890 is an unquoted service path vulnerability in LogonExpert 8.1, affecting the LogonExpertSvc service that runs with LocalSystem privileges. This flaw, mapped to CWE-428, arises from the service binary path not being properly quoted, enabling exploitation during service startup.
A local attacker with low privileges (PR:L) can exploit this vulnerability with low complexity (AC:L) by placing a malicious executable in an intermediate directory along the unquoted service path. Upon service restart, the system may execute the attacker's binary with LocalSystem privileges instead, achieving high confidentiality, integrity, and availability impacts (C:H/I:H/A:H), as reflected in the CVSS v3.1 base score of 7.8 (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H).
Advisories, including one from VulnCheck, describe the unquoted path in LogonExpertSvc. A proof-of-concept exploit is available on Exploit-DB (ID 49586). Vendor resources from Softros include a download link for LogonExpertSetup64.msi, but no specific patch or mitigation details are outlined in the references.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-4296
Vulnerability details
LogonExpert 8.1 contains an unquoted service path vulnerability in the LogonExpertSvc service running with LocalSystem privileges. Attackers can exploit the unquoted path to place malicious executables in intermediate directories, potentially gaining elevated system access during service startup.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Direct match to unquoted service path exploitation (CWE-428) enabling path interception for privilege escalation via malicious binary placement in intermediate directories.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Mandates secure configuration settings for system components like services, directly requiring quoted binary paths to prevent unquoted service path exploitation.
Requires timely identification, reporting, and correction of flaws such as the unquoted path in LogonExpertSvc to eliminate the vulnerability.
Provides vulnerability scanning to detect unquoted service path vulnerabilities like CVE-2021-47890 and enables remediation before local exploitation.