“This vulnerability is now under mass exploitation.” Citrix Bleed bug bites hard

Enlarge (credit: Getty Images)

A vulnerability that allows attackers to bypass multifactor authentication and access enterprise networks using hardware sold by Citrix is under mass exploitation by ransomware hackers despite a patch being available for three weeks.

Citrix Bleed, the common name for the vulnerability, carries a severity rating of 9.4 out of a possible 10, a relatively high designation for a mere information-disclosure bug. The reason: the information disclosed can include session tokens, which the hardware assigns to devices that have already successfully provided credentials, including those providing MFA. The vulnerability, tracked as CVE-2023-4966 and residing in Citrix’s NetScaler Application Delivery Controller and NetScaler Gateway, has been under active exploitation since August. Citrix issued a patch on October 10.

Repeat: This is not a drill

Attacks have only ramped up recently, prompting security researcher Kevin Beaumont on Saturday to declare: “This vulnerability is now under mass exploitation.” He went on to say, “From talking to multiple organizations, they are seeing widespread exploitation.”