Cisco warns of a second IOS XE zero
Vulnerabilities mentionedAll →
| CVE | Vulnerability | CVSS | EPSS | Flags | Affected | Exposure | Published |
|---|---|---|---|---|---|---|---|
| CVE-2023-20198 | Unauthenticated Privilege Escalation in Cisco IOS XE Web UI (Actively Exploited) 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. | 10.0 | 100% | KEV |
| large≈40,000–50,000 internet-exposed IOS XE devices at the time of disclosure (public scan data), within an IOS XE install base in the millions | |
| CVE-2023-20273 | Authenticated Command Injection (Root) in Cisco IOS XE Web UI CVE-2023-20273 is an OS command injection flaw (CWE-78) in the web UI feature of Cisco IOS XE Software, caused by insufficient input validation. An authenticated, remote attacker triggers it by sending crafted input to the web UI, and a successful exploit injects commands that run on the underlying operating system with root privileges, yielding full device compromise (in the October 2023 mass-exploitation campaign it was typically chained with the unauthenticated CVE-2023-20198 to obtain initial access and install a persistent implant). Any Cisco IOS XE device with the web UI enabled and reachable from the internet or an untrusted network is affected; this data does not specify the affected release ranges, which are enumerated in Cisco's advisory. Exploitation is confirmed in the wild: CISA added the flaw to the KEV on 2023-10-23 with BOD 23-02 response actions, EPSS is ~90% (100th percentile), and IOS XE edge devices remain recurring targets of Chinese-nexus espionage campaigns (e.g., Salt Typhoon activity against telecoms). Do: Upgrade affected devices to a fixed IOS XE release per Cisco's advisory; as an interim mitigation, disable the HTTP/HTTPS server (ip http server / ip https server) or restrict Web UI access to trusted hosts only. Per BOD 23-02, hunt for compromise on any exposed device — check for unexpected level-15 local accounts and the implant.lua backdoor in flash memory — and immediately report positive findings to CISA. | 7.2 | 90% | KEV |
| mass≈100,000+ internet-exposed IOS XE devices (public scans observed ~40,000+ compromised within days of disclosure) |
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Cisco found a second IOS XE zero-day vulnerability, tracked as CVE-2023-20273, which is actively exploited in attacks in the wild.
Cisco last week warned customers of a zero-day vulnerability, tracked as CVE-2023-20198 (CVSS score 10), in its IOS XE Software that is actively exploited in attacks. The IT giant found the vulnerability during the resolution of multiple Technical Assistance Center (TAC) support cases.
Threat actors have exploited the recently disclosed critical zero-day vulnerability (CVE-2023-20198) to compromise thousands of Cisco IOS XE devices, security firm VulnCheck warned.
The vulnerability can be exploited by an attacker to gain administrator privileges and take over vulnerable routers.
The advisory published by the vendor states that the exploitation of the vulnerability allows a remote, unauthenticated attacker to create an account on an affected system with privilege level 15 access.
“Cisco is aware of active exploitation of a previously unknown vulnerability in the web UI feature of Cisco IOS XE Software when exposed to the internet or to untrusted networks.” reads the advisory published by the company. “This vulnerability allows a remote, unauthenticated attacker to create an account on an affected system with privilege level 15 access. The attacker can then use that account to gain control of the affected system.”
The flaw affects physical and virtual devices running with the Web User Interface (Web UI) feature enabled and that have the HTTP or HTTPS Server feature in use.
The company urges administrators to check the system logs for the presence of any of the following log messages where the user could be cisco_tac_admin, cisco_support, or any configured, local user that is unknown to the network.
Cisco recommends admins to disable the HTTP server feature on systems exposed on the Internet.
Researchers from LeakIX used the indicators of compromise (IOCs) released by Cisco Talos and found around 30k Cisco IOS XE devices (routers, switches, VPNs) that were infected by exploiting the CVE-2023-20198. Most of the infected devices were in the United States, the Philippines, Chile, and Mexico.
CERT Orange also found a similar number of compromised Cisco IOS XE devices (over 34.5K) using the same IoCs.
Cisco new discovered a second actively exploited IOS XE zero-day vulnerability tracked as CVE-2023-20273.
While investigating attacks exploiting the flaw CVE-2023-20198, Cisco noticed attacks on systems patched against this issue, a circumstance that suggested that threat actors were exploiting a second zero-day flaw.
“Our investigation has determined that the actors exploited two previously unknown issues.” reads the advisory published by the company. “The attacker first exploited CVE-2023-20198 to gain initial access and issued a privilege 15 command to create a local user and password combination. This allowed the user to log in with normal user access.
The attacker then exploited another component of the web UI feature, leveraging the new local user to elevate privilege to root and write the implant to the file system. Cisco has assigned CVE-2023-20273 to this issue.
- CVE-2023-20198 has been assigned a CVSS Score of 10.0.
- CVE-2023-20273 has been assigned a CVSS Score of 7.2.”
The IT giant has now addressed both zero-day vulnerabilities and also provided mitigations for them.
| Cisco IOS XE Software Release Train | First Fixed Release | Available |
|---|---|---|
| 17.9 | 17.9.4a | Yes |
| 17.6 | 17.6.6a | TBD |
| 17.3 | 17.3.8a | TBD |
| 16.12 (Catalyst 3650 and 3850 only) | 16.12.10a | TBD |
Cyber security firms observed a rapid drop in the number of infected devices, but the root cause was the attempt of the attackers to hide their infection as reported by Shadowserver Foundation.
— Shadowserver (@Shadowserver) October 23, 2023UPDATE: Improved Cisco IOS XE Web UI CVE-2023-20198 implant detection, after threat actor modified their compromised device config (hat tip to @foxit)
30,487 unique IPs on 2023-10-23
Latest data in tonight's compromised website report. Dashboard stats updated after end of day. pic.twitter.com/7SjqduAaGA
“Please note that a potential trace cleaning step is underway to hide the implant (following exploitation of #CVE-2023-20198)” reported CERT Orange Cyberdefense. “Even if you have disabled your WebUI, we recommend that you carry out an investigation to make sure that no malicious users has been added and that its configuration has not been altered”
Even if you have disabled your WebUI, we recommend that you carry out an investigation to make sure that no malicious users has been added and that its configuration has not been altered 2/2
— CERT Orange Cyberdefense (@CERTCyberdef) October 21, 2023
At the time of this publishing, it is still unclear who is behind these attacks.
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