CVE-2023-20198
About
Cisco is providing an update for the ongoing investigation into observed exploitation of the web UI feature in Cisco IOS XE Software. We are updating the list of fixed releases and adding the Software Checker. Our investigation has determined that the actors exploited two previously unknown issues. 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. Both of these CVEs are being tracked by CSCwh87343.
Rainforest analyst review
The web UI feature of Cisco IOS XE contains an authentication bypass that lets an unauthenticated attacker who can reach the HTTP/HTTPS management interface create a local account at full privilege level 15. That account is legitimate as far as the device is concerned, so the attacker logs in normally and then chains a second web UI flaw, CVE-2023-20273, to elevate to root and write an implant to the filesystem. The first flaw is the front door; the second turns access into persistent control.
IOS XE runs on an enormous installed base of Cisco routers and switches, and this was exploited as a zero-day in October 2023, implanting tens of thousands of devices in a matter of days. These are core network devices, so a rogue privileged account and a filesystem implant mean an attacker sits astride the traffic. Disable the HTTP server feature where it isn't needed, apply the fixed releases, and hunt actively: check for unexpected local accounts and use Cisco's guidance to detect the implant, since a patch does not evict an attacker who is already resident.
References
Related CVEs
No related CVEs.
Frequently asked questions
What is CVE-2023-20198?
Cisco is providing an update for the ongoing investigation into observed exploitation of the web UI feature in Cisco IOS XE Software. We are updating the list of fixed releases and adding the Software Checker. Our investigation has determined that the actors exploited two previously unknown issues.
How severe is CVE-2023-20198?
CVE-2023-20198 carries a CVSS 3.1 base score of 10, rated critical. On the Rainforest Risk Index — which weighs the severity alongside how easy the flaw is to reach and how broad its impact is — it scores 100 out of 100, in the critical band.
How is CVE-2023-20198 exploited?
According to the CVSS vector (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H): attack vector Network, attack complexity Low, privileges required None, user interaction None. Impact on confidentiality High, integrity High and availability High.
Which products are affected by CVE-2023-20198?
Public advisories list the following as affected: allen-bradley stratix 5200, allen-bradley stratix 5200 firmware, allen-bradley stratix 5800, allen-bradley stratix 5800 firmware, ios xe. Check the references on this page for the exact versions each vendor confirms.
How do I fix CVE-2023-20198?
Apply the fix the vendor published — the references on this page link to the primary advisories and patches. When patching can't happen right away, reduce the exposure of the affected component and watch it for exploitation attempts. Rainforest customers see this vulnerability correlated to their own assets and prioritized by real exposure, not by score alone.
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