Critical Cisco Unity Connection flaw gives attackers root privileges. Patch now! (CVE-2024-20272)

CVE-2023-20198 is a critical (CVSS 10.0) unauthenticated privilege escalation flaw in the web UI of Cisco IOS XE software, triggered by sending crafted network requests to the exposed web management interface. An attacker with no credentials can use the flaw to gain initial access and issue a privilege 15 command, creating a local user with normal login access; the attacker then chained CVE-2023-20273 (CVSS 7.2) to elevate that account to root and write an implant to the file system. Successful exploitation yields full administrative control of the device, including persistence via the planted implant, on Cisco IOS XE devices with the web UI enabled and reachable from the internet or untrusted networks, including Rockwell Automation Allen-Bradley Stratix 5200 and 5800 switches running IOS XE. Exploitation is confirmed in the wild: the flaw was added to CISA's KEV on 2023-10-16 with a BOD 23-02 directive, EPSS stands at 99.6% (100th percentile), and ongoing campaigns (including the 'BADCANDY' activity flagged by Australia's ASD and Cisco-related telecom intrusions attributed to Salt Typhoon) have been reported.

Do: Upgrade affected devices to the fixed releases listed in Cisco's advisory (use Cisco's Software Checker) and, as immediate mitigation, disable the web UI or restrict it to trusted networks/addresses only. Check for compromise by looking for unexpected local user accounts and the implant artifacts Cisco identified (unexpected cisco_tac_alarm.log and cisco_tac.log files in /tmp or /usr/binos/conf), and immediately report positive findings to CISA per BOD 23-02. Keep in mind that patching alone does not remove a root implant, so devices with evidence of compromise should be reimaged or otherwise cleaned per vendor instructions.

Cisco Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD) contain an authentication weakness (CWE-288) that allows an unauthenticated, remote attacker to conduct brute-force attacks against the SSL VPN login interface to guess valid username and password combinations, and to establish a clientless SSL VPN session as an unauthorized user under certain configurations. The attack is triggered simply by sending repeated or crafted authentication attempts to an internet-facing remote-access VPN endpoint, and vendor guidance centers on the group-lock and vpn-simultaneous-logins settings. A successful attempt gives the attacker VPN access, typically allowing them to reach the internal network as a legitimate user, which makes the flaw a common foothold for follow-on attacks including ransomware. Any organization operating a Cisco ASA or FTD with remote-access/clientless SSL VPN exposed to the internet is affected. The vulnerability was added to CISA's Known Exploited Vulnerabilities catalog on 2023-09-13 with known ransomware use, and EPSS assigns it a 25.6% probability of exploitation within 30 days (98th percentile).

Do: Apply the mitigations in the Cisco advisory: configure group-lock and per-user vpn-simultaneous-logins restrictions as directed, and update ASA/FTD to the fixed releases listed there; if the device is end-of-support/unsupported, discontinue or isolate it. Prioritize internet-facing VPN concentrators given the KEV listing and known ransomware use, and review VPN logs for unusual failed-login bursts and unexpected clientless SSL VPN sessions.

A vulnerability in the web-based management interface of Cisco Unity Connection could allow an unauthenticated, remote attacker to upload arbitrary files to an affected system and execute commands on the underlying operating system. This vulnerability is due to a lack of authentication in a specific API and improper validation of user-supplied data. An attacker could exploit this vulnerability by uploading arbitrary files to an affected system. A successful exploit could allow the attacker to store malicious files on the system, execute arbitrary commands on the operating system, and elevate privileges to root.