CVE-2019-5185

/// Technical description

An exploitable stack buffer overflow vulnerability vulnerability exists in the iocheckd service "I/O-Check" functionality of WAGO PFC 200. An attacker can send a specially crafted packet to trigger the parsing of this cache file. At 0x1ea28 the extracted state value from the xml file is used as an argument to /etc/config-tools/config_interfaces interface=X1 state=<contents of state node> using sprintf(). The destination buffer sp+0x40 is overflowed with the call to sprintf() for any state values that are greater than 512-len("/etc/config-tools/config_interfaces interface=X1 state=") in length. Later, at 0x1ea08 strcpy() is used to copy the contents of the stack buffer that was overflowed sp+0x40 into sp+0x440. The buffer sp+0x440 is immediately adjacent to sp+0x40 on the stack. Therefore, there is no NULL termination on the buffer sp+0x40 since it overflowed into sp+0x440. The strcpy() will result in invalid memory access. An state value of length 0x3c9 will cause the service to crash.

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References