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Citrix Warns NetScaler ADC Customers of New Zero-Day Exploitation

Citrix is aware of attacks exploiting two new NetScaler ADC and Gateway zero-day vulnerabilities tracked as CVE-2023-6548 and CVE-2023-6549.

Citrix NetScaler zero-day

A security bulletin published by Citrix on Tuesday informs customers that two new zero-day vulnerabilities affecting its NetScaler ADC and Gateway products have been exploited in attacks.

One of the flaws, tracked as CVE-2023-6548, is a medium-severity issue that allows a low-privileged authenticated attacker to remotely execute arbitrary code on the management interface. 

The second vulnerability, CVE-2023-6549, is a high-severity issue that can be exploited for denial-of-service (DoS) attacks.

“Exploits of these CVEs on unmitigated appliances have been observed,” Citrix warned, urging customers to install the available patches as soon as possible. 

Exploitation of CVE-2023-6548 requires access to the appliance’s management interface, and the DoS flaw can only be exploited against devices configured as a gateway or AAA virtual server.

“Cloud Software Group strongly recommends that network traffic to the appliance’s management interface is separated, either physically or logically, from normal network traffic. In addition, we recommend that you do not expose the management interface to the internet, as explained in the secure deployment guide. Removing such exposure to the internet greatly reduces the risk of exploitation of this issue,” Citrix urged customers.

There does not appear to be any information on the attacks. Based on the few details that are available, the vulnerabilities may be exploited in highly targeted attacks and possibly chained with other security holes.

“The impact from these two new zero-day vulnerabilities is not expected to be as significant as CitrixBleed,” Tenable experts said on Tuesday. 

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Security researcher Kevin Beaumont also believes impact will be limited, at least based on the information that is currently available. 

It’s not uncommon for threat actors to target NetScaler appliances in their attacks, which can result in hundreds or even thousands of instances getting compromised. 

Related: Citrix, Gov Agencies Issue Fresh Warnings on CitrixBleed Vulnerability

Related: Recent NetScaler Vulnerability Exploited as Zero-Day Since August

Related: Citrix Patches Critical NetScaler ADC, Gateway Vulnerability

Related: Credential Harvesting Campaign Targets Unpatched NetScaler Instances

Written By

Eduard Kovacs (@EduardKovacs) is a managing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.


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