The following analytic identifies potential exploitation of a previously unknown vulnerability in the Web User Interface (Web UI) feature of Cisco IOS XE software (CVE-2023-20198). Successful exploitation allows an attacker to create an account on the affected device with privilege level 15 access, granting them full control of the compromised device. The detection is based on the observation of suspicious account creation and subsequent actions, including the deployment of an implant consisting of a configuration file. The implant is saved under the file path //usr//binos//conf//nginx-conf//cisco_service.conf and is not persistent, meaning a device reboot will remove it, but the newly created local user accounts remain active even after system reboots. The new user accounts have level 15 privileges, meaning they have full administrator access to the device. This privileged access to the devices and subsequent creation of new users is tracked as CVE-2023-20198.
- Type: TTP
- Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- Datamodel: Web
- Last Updated: 2023-10-17
- Author: Michael Haag, Splunk
- ID: 07c36cda-6567-43c3-bc1a-89dff61e2cd9
Kill Chain Phase
- CIS 13
|CVE-2023-20198||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. 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.|
For steps to close the attack vector for this vulnerability, see the Recommendations section of this advisory
|Cisco will provide updates on the status of this investigation and when a software patch is available.||None|
1 2 3 4 5 6 | tstats count min(_time) as firstTime max(_time) as lastTime from datamodel=Web where Web.url IN ("/webui/logoutconfirm.html?logon_hash=*") Web.http_method=POST Web.status=200 by Web.http_user_agent, Web.status Web.http_method, Web.url, Web.url_length, Web.src, Web.dest, sourcetype | `drop_dm_object_name("Web")` | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `cisco_ios_xe_implant_access_filter`
The SPL above uses the following Macros:
cisco_ios_xe_implant_access_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
List of fields required to use this analytic.
How To Implement
This detection requires the Web datamodel to be populated from a supported Technology Add-On like Splunk for Apache, Splunk for Nginx, or Splunk for Palo Alto.
Known False Positives
False positives may be present, restrict to Cisco IOS XE devices or perimeter appliances. Modify the analytic as needed based on hunting for successful exploitation of CVE-2023-20198.
Associated Analytic Story
|81.0||90||90||Possible exploitation of CVE-2023-20198 against $dest$ by $src$.|
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.
source | version: 1