Cybersecurity Advisories

CVE-2023-20198: Cisco IOS XE Software Web UI Privilege Escalation Vulnerability

October 22nd, 2023 Update: Cisco has released fixes for CVE-2023-20198. Customers are advised to upgrade to an appropriate fixed software release.

Cisco is warning of a critical severity zero-day vulnerability affecting Cisco IOS XE that 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. Tracked as CVE-2023-20198 (CVSSv3 score: 10.0 – Critical), the actively exploited flaw impacts the software’s Web UI feature and affects both physical and virtual devices running IOS XE when they are exposed to the internet and have the HTTP or HTTPS Server feature enabled. At the time of writing, there is no patch available, however Cisco will provide updates on the status and when a software patch is available. Customers are strongly recommended to disable the HTTP Server feature on all internet-facing systems and check for malicious activity in the form of newly created users on its devices.

The issue was discovered after Cisco detected malicious activity on a customer’s device in September 2023, where an authorized user created a local user account under the username “cisco_tac_admin” from a suspicious IP address. This activity ended on October 1, 2023. Another set of related activities occurred on October 12, 2023, where an unauthorized user created a local user account under the name “cisco_support” from a different IP address. This is claimed to have been followed by a series of actions that ended in the deployment of a Lua-based implant that allows the actor to execute arbitrary commands at the system level or IOS level. These clusters of activity were assessed to likely be carried out by the same threat actor.

The installation of the implant is carried out by exploiting an older vulnerability, CVE-2021-1435, which is a patched command injection flaw that impacted the web UI of Cisco IOS XE Software. The vulnerability would allow an authenticated attacker to inject arbitrary code that would be executed as the root user. It was observed that even on devices that were fully patched against CVE-2021-1435, threat actors were still able to deploy their implant. At the time of writing, it is not known how they were able to do so.

No proof-of-concept code was found to be publicly available for CVE-2023-20198. Based on research using the Shodan search engine, there are nearly 40,000 Cisco devices that have web UI exposed to the internet.

SecurIT360 SOC Managed Services 

If you utilize our SOC Managed Services, here are the actions we are taking to help detect this activity: 

MDR Services 

  • We utilize several threat feeds that are updated frequently on a daily basis.
  • In addition to our automatic threat feeds, we have added indicators related to known malicious threat actors into our MDR solution, FortiSIEM.

EDR Services 

  • In addition to ongoing vendor IoC updates, we have implemented known IoC information to help with detection. 

Additionally, we are running a Nessus external scan to search for any affected hosts and will report if we find anything.

Indicators are provided in the Indicators of Compromise section below for your reference.

As always, if we detect activity related to these exploits, we will alert you when applicable. 

Affected Products

This vulnerability affects Cisco IOS XE Software if the web UI feature is enabled. The web UI feature is enabled through the ip http server or ip http secure-server commands.


According to Cisco, customers are strongly recommended to 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. If both the HTTP server and HTTPS server are in use, both commands are required to disable the HTTP Server feature.

The following decision tree can be used to help determine how to triage an environment and deploy protections:

  • Are you running IOS XE?
    • No. The system is not vulnerable. No further action is necessary.
    • Yes. Is ip http server or ip http secure-server configured?
      • No. The vulnerability is not exploitable. No further action is necessary.
      • Yes. Do you run services that require HTTP/HTTPS communication (for example, eWLC)?
        • No. Disable the HTTP Server feature.
        • Yes. If possible, restrict access to those services to trusted networks.

Cisco Advisory

Cisco IOS XE Software Web UI Privilege Escalation Vulnerability

Cisco IOS XE Implant Scanner

VulnCheck has released a scanner to detect the implant on affected devices. See: cisco-ios-xe-implant-scanner

Indicators of Compromise



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Cybersecurity Advisories

Microsoft’s October 2023 Patch Tuesday Addresses 3 Zero-Days and Over 100 Flaws

Microsoft released security updates for 103 vulnerabilities, including forty-five RCE bugs and three actively exploited zero-day flaws. Of the 103 flaws, 13 are rated Critical and 90 are rated Important in severity. Notable vulnerabilities are listed below. For the full list, see Microsoft CVE Summary.

CVE-2023-36563 – Microsoft WordPad Information Disclosure Vulnerability

Microsoft released fixes for an actively exploited information disclosure vulnerability in Microsoft WordPad that can be used to steal NTLM hashes when opening a document. Tracked as CVE-2023-36563 (CVSSv3 score: 6.5 – Medium), an unauthenticated, remote attacker could exploit this vulnerability using social engineering in order to convince a victim to open a link or download a malicious file and run it on the vulnerable system. As an alternative, an attacker could execute a specially crafted application to exploit the flaw after gaining access to a vulnerable system. Successful exploitation could lead to the disclosure of NTLM hashes. Admins should consider blocking outbound NTLM over SMB on Windows 11 to significantly hinder NTLM-relay exploits.

Microsoft announced last month that Word Pad is no longer being updated and will be removed in a future version of Windows, although no specific timeline has yet been given. Microsoft recommends Word as a replacement for WordPad.

  • For more information, see: Microsoft WordPad Information Disclosure Vulnerability

CVE-2023-41763 – Skype for Business Elevation of Privilege Vulnerability

Microsoft has fixed an actively exploited Elevation of Privilege flaw in Skype for Business that can be used by sending a specially crafted network call to a vulnerable Skype for Business server. Tracked as CVE-2023-41763 (CVSSv3 score: 5.3 – Medium), successful exploitation would result in the disclosure of IP addresses and/or port numbers, which could be used to gain access to internal networks.

CVE-2023-44487 – HTTP/2 Rapid Reset Attack

Microsoft released mitigations for a new zero-day DDoS technique called HTTP/2 Rapid Reset Attack. Tracked as CVE-2023-44487, (CVSSv3 score: 5.3 – Medium), attackers can make hundreds of thousands of requests and immediately cancel them with a reset stream. This avoids limits on the number of streams accepted and can lead to CPU exhaustion on the server attempting to clean up the canceled streams. By using the “request, cancel, request, cancel” pattern at scale, threat actors overwhelm websites and can make anything that uses HTTP/2 go offline.

According to Google, the protocol does not require the client and server to coordinate the cancelation in any way, the client may do it unilaterally. The client may also assume that the cancellation will take effect immediately when the server receives the RST_STREAM frame, before any other data from that TCP connection is processed. As the feature is built into the HTTP/2 standard, there is no fix for the technique that can be implemented other than rate limiting or blocking the protocol. While the DDoS has the potential to impact service availability, it alone does not lead to the compromise of customer data.


All providers who have HTTP/2 services should assess their exposure to this issue. Software patches and updates for common web servers and programming languages may be available to apply now or in the near future. Microsoft’s mitigation steps in the advisory are to disable the HTTP/2 protocol on your web server. Additional information and protections are detailed in a dedicated article on HTTP/2 Rapid Reset.

SecurIT360 SOC Managed Services 

If you utilize our SOC Managed Services for MDR and/or EDR, we are actively monitoring the release of IoCs related to these CVE’s. Along with standard vendor threat feed and signature updates, we will proactively upload these to our SOC tools if applicable.

As always, if we detect activity related to these exploits, we will alert you if warranted.

Additionally, we are running a Nessus external scan to search for any affected hosts and will report if we find anything.

Please feel free to contact the SOC via email ( or telephone (844-474-1244) if you have any questions or concerns.

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