CVE-2019-5177

Vulnerability

A stack buffer overflow vulnerability exists in the iocheckd service 'I/O-Check' functionality of WAGO PFC 200 firmware version 03.02.02(14). The destination buffer at sp+0x440 is overflowed by the sprintf() call when a domainname value exceeds 1024 - len('/etc/config-tools/edit_dns_server domain-name=') bytes. The vulnerability is triggered during parsing of a specially crafted XML cache file stored at /tmp/iocheckCache.xml, which is globally writable [1].

Exploitation

An attacker with write access to /tmp (available to all users) can place a malicious XML file at /tmp/iocheckCache.xml. Sending a BC_SaveParameter message to the iocheckd service causes the cache file to be parsed, leading to the stack buffer overflow when a long domainname value is processed [1].

Impact

Successful exploitation results in a stack buffer overflow that can be leveraged for arbitrary code execution on the device. The CVSSv3 score of 8.8 (AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H) indicates high impact on confidentiality, integrity, and availability, with a scope change [1].

Mitigation

No fixed version is disclosed in the available reference [1]. Users should contact WAGO for firmware updates or apply workarounds such as restricting write access to /tmp if possible. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog as of the publication date.