This week Cisco patched three critical vulnerabilities affecting its operating system IOS XE,  two of them are remote code execution flaws that could be exploited by an attacker to gain full control over vulnerable systems.

Cisco March 2018 Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled Publication addressed 22 vulnerabilities, 3 of them rated as critical and 19 as high.

Let’s give a close look at the critical vulnerabilities.

The first issue. tracked as CVE-2018-0151, is an IOS and IOS XE Software Quality of Service Remote Code Execution Vulnerability.

“A vulnerability in the quality of service (QoS) subsystem of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition or execute arbitrary code with elevated privileges.” reads the advisory published by Cisco.

“The vulnerability is due to incorrect bounds checking of certain values in packets that are destined for UDP port 18999 of an affected device. An attacker could exploit this vulnerability by sending malicious packets to an affected device”

IOS XE

The second vulnerability tracked as CVE-2018-0171 affects the Smart Install feature of Cisco IOS Software and Cisco IOS XE Software, it could be exploited by an unauthenticated, remote attacker to cause a reload of a vulnerable device or to execute arbitrary code on an affected device.

“The vulnerability is due to improper validation of packet data. An attacker could exploit this vulnerability by sending a crafted Smart Install message to an affected device on TCP port 4786.” reads the security advisory published by Cisco.

“A successful exploit could allow the attacker to cause a buffer overflow on the affected device, which could have the following impacts:

  • Triggering a reload of the device
  • Allowing the attacker to execute arbitrary code on the device
  • Causing an indefinite loop on the affected device that triggers a watchdog crash”

The third flaw affects the Cisco IOS XE Software is due to an undocumented user account “with privilege level 15” hat has a default username and password.

The issue tracked as CVE-2018-0150 could be exploited by an unauthenticated, remote attacker to log in to a device running an affected release of Cisco IOS XE Software with the default credentials.

“A vulnerability in Cisco IOS XE Software could allow an unauthenticated, remote attacker to log in to a device running an affected release of Cisco IOS XE Software with the default username and password that are used at initial boot.” reads the security advisory published by Cisco.

“The vulnerability is due to an undocumented user account with privilege level 15 that has a default username and password. An attacker could exploit this vulnerability by using this account to remotely connect to an affected device. A successful exploit could allow the attacker to log in to the device with privilege level 15 access.”