Cisco Web UI Vulnerability Exploited Massly, Impacting Over 40K Devices

Cisco Web UI Vulnerability Exploited Massly, Impacting Over 40K Devices

It is unclear how long Cisco will take to release a patch.

The US had the most compromised devices (4,659) with a backdoor installed as a result of the Cisco Web UI vulnerability followed by the Philippines (over 3,200).


Cisco released a security advisory on October 16 to warn users about a critical zero-day privilege escalation vulnerability in its IOS XE Web UI software.

As per Censys, the company tracking the vulnerability, by October 18 the number of infections had increased from the previously reported 34,140 to 41,983 hosts, while 34,140 had backdoor installed

It is tracked as CVE-2023-20198 and has been used to exploit tens of thousands of devices.

The US had the highest number of compromised devices followed by the Philippines.

A critical cybersecurity threat disclosed by Cisco has resulted in mass exploitation of its devices, with the number of impacted systems surpassing 40,000 hosts worldwide. Nonprofit security group Shadowserver has detected over 32,800 devices compromised so far.

On the other hand, Censys has been tracking this vulnerability and in its blog post, the company explained that due to active exploitation of this security flaw tens of thousands of devices could be affected.

The company scanned the impacted Cisco devices and found that most belonged to telecom firms offering internet services to business and home users, including AT&T. The US had the highest number of compromised devices with a backdoor installed (4,659) followed by the Philippines (over 3,200). had reported that the vulnerability, tracked as CVE-2023-20198, was discovered in the Cisco IOS XE software’s Web UI feature. Cisco warned customers about the vulnerability affecting Cisco RV320 and RV325 routers, explaining that it allows a remote unauthorized attacker to create an account on the compromised system with privilege level 15 access and go on to gain full control of the device. 

The vulnerability affects the IOS XE Software Web UI feature because it is enabled by default in the devices. Cisco recommends users disable the HTTP server feature on every internet-connected system to prevent exploitation. Attackers exploiting this flaw are hijacking routers from telecom firms. Cisco has confirmed that since at least mid-September, threat actors have been exploiting it as a zero-day.

The vulnerability was first discovered in March 2023, and an uptick in attacks exploiting it was observed from mid-September. Moreover, a highly sophisticated actor is suspected to be exploiting it, which hints at the launch of a targeted and coordinated campaign while Cisco is still working on a patch to fix it.

In its threat advisory published on October 16th, 2023, Cisco stated that the actor exploited the old, already patched vulnerability (CVE-2021-1435) to install the implant after obtaining access to the device.

“We have also seen devices fully patched against CVE-2021-1435 getting the implant successfully installed through an as-of-yet undetermined mechanism.”


It is a serious security threat as the vulnerability has the highest criticality score of 10. The IOS XE software is an essential component of Cisco switches, wireless controller products, and routers. The vulnerability is critical enough to enable a complete takeover of Cisco devices, granting threat actors the ability to effortlessly monitor network traffic or present phishing pages loaded with harmful malware.

Reportedly, 469 of the compromised devices were registered at AT&T for residential and business clients. The company uses enterprise-grade Cisco XE routers, so small-sized organizations and individuals would likely be vulnerable to this threat instead of large corporations.

The risks posed by the vulnerability are wide-ranging, as attackers can leverage access to compromised devices to disrupt network operations, steal sensitive data, and launch new attacks against other systems on the network.

It is unclear how long Cisco will take to release a patch. Meanwhile, users must scan their devices for infection and disable the HTTP server feature, implement network segmentation, and monitor network traffic for suspicious activity.

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