Actively exploited vulnerability

Citrix Application Delivery Controller (ADC), Gateway, and SD-WAN WANOP Appliance: security bypass flaw under attack

CVE-2020-8193 · Citrix ADC, Gateway, and SD-WAN WANOP Appliance Authorization Bypass Vulnerability

Business software6.5 medium

What is affected

Citrix Application Delivery Controller (ADC), Gateway, and SD-WAN WANOP Appliance is mostly run by companies, schools and public bodies, not on home computers. You are unlikely to have it yourself, but organisations that hold your data may. Breaches that start with flaws like this one are how personal data ends up leaked.

Citrix ADC, Citrix Gateway, and multiple Citrix SD-WAN WANOP appliance models contain an authorization bypass vulnerability that may allow unauthenticated access to certain URL endpoints. The attacker must have access to the NetScaler IP (NSIP) in order to perform exploitation.

CISA's description

What an attacker can do

This is a security bypass flaw. It lets an attacker slip past a built-in protection, so warnings and checks that normally stop malicious content never appear.

How it is reached
Over the internet or network
Access the attacker needs
No account needed
Does the victim have to do something?
No, works without the victim doing anything

What to do

  1. At home: nothing to install. Keep your own devices updated and use a different password for every service, so that a breach at one organisation does not open your other accounts.
  2. If you administer Citrix Application Delivery Controller (ADC), Gateway, and SD-WAN WANOP Appliance at work: apply the vendor's fix or mitigation now and review logs for signs of compromise, because the flaw was being exploited before it was listed.
  3. If the product is past its support date and no fix exists, take it off the internet or retire it.

Apply updates per vendor instructions.

Action required by CISA for US federal agencies

How urgent is it

CISA added this vulnerability to its Known Exploited Vulnerabilities catalogue on November 3, 2021, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by May 3, 2022, a deadline that has already passed. That deadline does not bind anyone else, but it shows how seriously the agency rates it.

The EPSS model estimates a 88% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 99.8% of all scored vulnerabilities.

Its CVSS severity score is 6.5 out of 10 (medium), as recorded in the US National Vulnerability Database.

Technical description

Improper access control in Citrix ADC and Citrix Gateway versions before 13.0-58.30, 12.1-57.18, 12.0-63.21, 11.1-64.14 and 10.5-70.18 and Citrix SDWAN WAN-OP versions before 11.1.1a, 11.0.3d and 10.2.7 allows unauthenticated access to certain URL endpoints.

NIST National Vulnerability Database
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