Cisco has released a new round of patches for a potentially serious Webex vulnerability first addressed one month ago.
The vulnerability in question is tracked as CVE-2018-15442 and the Counter Hack researchers who discovered it have dubbed it WebExec. It affects releases prior to 33.6.4 of the Cisco Webex Meetings desktop app, and Webex Productivity Tools releases 32.6.0 and later, prior to 33.0.6.
Cisco first released fixes on October 24, when the researchers made their findings public along with proof-of-concept (PoC) code.
The security hole, caused by insufficient validation of user-supplied parameters, allows a local and authenticated attacker to execute arbitrary commands with SYSTEM privileges. However, Cisco warned that remote exploitation may also be possible in Active Directory deployments.
Days after the details of the vulnerability were made public, researchers at SecureAuth discovered that Cisco’s patch was incomplete – it can be bypassed using a technique known as DLL hijacking.
“The vulnerability can be exploited by copying to an a local attacker controller folder, the ptUpdate.exe binary. Also, a malicious dll must be placed in the same folder, named wbxtrace.dll,” SecureAuth wrote in an advisory published on Tuesday. “To gain privileges, the attacker must start the service with the command line: sc start webexservice install software-update 1 ‘attacker-controlled-path’ (if the parameter 1 doesn’t work, then 2 should be used).”
SecureAuth notified Cisco on November 9 and the networking giant quickly confirmed the findings. Cisco on Tuesday released a new set of patches and updated its initial advisory to inform users of the incomplete patch.
“After an additional attack method was reported to Cisco, the previous fix for this vulnerability was determined to be insufficient. A new fix was developed, and the advisory was updated on November 27, 2018, to reflect which software releases include the complete fix,” Cisco wrote.
SecureAuth’s advisory contains PoC code demonstrating the company’s findings.