CISA’s Emergency Alert: Critical Citrix Flaw Lets Attackers Bypass Security in Minutes

A critical Citrix NetScaler vulnerability, CVE-2025-5777, has triggered an emergency alert from the U.S. Cybersecurity and Infrastructure Security Agency. The flaw is now confirmed as actively exploited, putting enterprise networks at immediate risk.

CISA’s inclusion of this vulnerability in its Known Exploited Vulnerabilities catalog signals a high-priority threat. Attackers can bypass authentication and access sensitive data in minutes if systems remain unpatched.

How did attackers exploit the Citrix NetScaler flaw so quickly?

CVE-2025-5777 stems from insufficient input validation in Citrix NetScaler ADC and Gateway products. When configured as a gateway or AAA virtual server, this flaw allows an out-of-bounds read, exposing memory contents to remote attackers.

Security researchers have dubbed the flaw "CitrixBleed 2" due to its resemblance to the notorious 2023 CitrixBleed incident. Attackers can repeatedly trigger the vulnerability, leaking new chunks of sensitive memory each time, including session tokens and authentication credentials.

Did you know?
The original CitrixBleed vulnerability in 2023 led to widespread breaches, prompting global enterprises to overhaul their remote access security strategies.

What immediate steps must enterprises take to secure their networks?

CISA requires all Federal Civilian Executive Branch agencies to implement mitigations by July 11, EST. We strongly urge all organizations, irrespective of their sector, to immediately patch the affected NetScaler appliances and forcefully terminate all active sessions to invalidate any stolen tokens.

Admins should inspect authentication logs for suspicious activity, especially requests to endpoints like /p/u/doAuthentication.do, and review responses for unexpected XML data. Because the vulnerability is a memory overread, it does not leave traditional malware traces, making detection challenging.

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CISA confirms active exploitation of CitrixBleed 2 vulnerability

Cybersecurity researchers and vendors are increasingly providing evidence that the wild is weaponizing CVE-2025-5777, prompting CISA's alert. Attackers have targeted NetScaler devices across multiple countries, using the flaw to hijack sessions and bypass multi-factor authentication.

On June 17, 2025, Citrix released a patch for the vulnerability. However, exploitation reports surfaced soon after, with security experts warning that unpatched systems could be compromised within minutes of exposure.

Sensitive enterprise data is at risk from authentication bypass attacks

Enterprise applications, VPNs, and cloud dashboards often use NetScaler devices as centralized access points. A successful attack could grant unauthorized access to internal networks, privileged admin interfaces, and sensitive data repositories, raising the risk of large-scale breaches.

Given the critical nature of this vulnerability, organizations must act decisively. The speed and scale of active exploitation points to the need for immediate remediation and vigilant monitoring of all authentication activity.

The cybersecurity landscape is evolving rapidly, and only proactive defenses will keep enterprise networks secure against the next wave of sophisticated attacks.