Cisco is aware of the active exploitation of this vulnerability, but there are no workarounds available.
Cisco has warned customers of a previously unknown vulnerability in the web UI feature of Cisco IOS XE Software that is being actively exploited by attackers. The vulnerability allows a remote, unauthenticated attacker to create an account on an affected system with privilege level 15 access, which could further allow them to gain full control of the device.
The vulnerability (CVE-2023-20198) affects Cisco IOS XE Software if the web UI feature is enabled, which is done by default. Cisco recommends that customers disable the HTTP Server feature on all internet-facing systems to mitigate the risk of exploitation.
In its security advisory, Cisco said that the company is aware of the active exploitation of this vulnerability, and there are no workarounds available. Cisco is working on a software patch to address the vulnerability, but a release date has not yet been announced.
John Bambenek, Principal Threat Hunter at Netenrich, a San Jose, Calif.-based security and operations analytics SaaS company commented on the advisory and warned that “The fact there isn’t a patch yet makes this issue all the more urgent and admins should take this opportunity to ensure their Cisco IOS devices either disable the Web UI or only have it accessible from private administrative LANs that are restricted to authorized users.”
Mayuresh Dani, Manager, Threat Research at Qualys, a Foster City, Calif.-based provider of disruptive cloud-based IT, security and compliance solutions stressed that Cisco has not provided the list of devices affected, which means that any switch, router or WLC running IOS XE and has the web UI exposed to the internet is vulnerable.”
Dani disclosed concerning statistics regarding Cisco devices with their web UI exposed to the internet. These findings indicate that more than 40,000 Cisco devices fall into this category, with the majority of them actively listening on port 80.
“Devices that have web UI and management services publicly exposed to the internet or to untrusted networks should be modified so that they are not exposed to untrusted networks by means of ACLs or other solutions. 2. Disable the web UI component on these devices,” Dani advised.
Indicators of Compromise
To determine whether a system may have been compromised, customers can check the system logs for the presence of the following log messages:
- %SYS-5-CONFIG_P: Configured programmatically by process SEP_webui_wsma_http from console as user on line
- %SEC_LOGIN-5-WEBLOGIN_SUCCESS: Login Success at 03:42:13 UTC Wed Oct 11 2023
Customers can also use the following command to check for the presence of the implant:
curl -k -X POST "https://systemip/webui/logoutconfirm.html?logon_hash=1"
If the request returns a hexadecimal string, the implant is present.
Recommendations
Cisco strongly recommends that customers disable the HTTP Server feature on all internet-facing systems. To disable the HTTP Server feature, use the no ip http server or no ip http secure-server command in global configuration mode.
Customers who cannot disable the HTTP Server feature should restrict access to those services to trusted networks.
Cisco is also working on a software patch to address the vulnerability, and customers are advised to apply the patch as soon as it is available.
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