CISA Warns of CitrixBleed 2 Vulnerability Exploited in Attacks

CISA has issued an urgent warning regarding a critical vulnerability in Citrix NetScaler ADC and Gateway products that is being actively exploited in cyberattacks. 

The vulnerability, tracked as CVE-2025-5777, has been added to CISA’s Known Exploited Vulnerabilities (KEV) catalog with an immediate remediation deadline of July 11, 2025.

Key Takeaways
1. CISA warns of actively exploited CVE-2025-5777 vulnerability in Citrix NetScaler ADC and Gateway products.
2. Out-of-bounds read vulnerability (CWE-125) affects Gateway and AAA virtual server configurations, causing memory overread.
3. Apply vendor mitigations by July 11, 2025, or discontinue product use if fixes unavailable.
4. Active exploitation threatens system compromise through sensitive memory access

Out-of-Bounds Read Vulnerability (CVE-2025-5777)

The identified security flaw is classified as an out-of-bounds read vulnerability stemming from insufficient input validation within the NetScaler architecture. 

According to CISA’s advisory, this vulnerability is categorized under CWE-125 (Out-of-bounds Read), which represents a class of software weaknesses where programs read data past the end or before the beginning of the intended buffer.

The technical impact of CVE-2025-5777 manifests as memory overread conditions when NetScaler systems are configured in specific operational modes. 

The vulnerability specifically affects deployments where NetScaler functions as a Gateway with VPN virtual server configurations, ICA Proxy services, CVPN implementations, or RDP Proxy setups. 

Additionally, systems configured with AAA (Authentication, Authorization, and Accounting) virtual servers are equally susceptible to exploitation.

CISA’s inclusion of this vulnerability in the KEV catalog indicates that threat actors are actively exploiting CVE-2025-5777 in real-world attack scenarios. 

The out-of-bounds read condition can potentially allow malicious actors to access sensitive memory contents, potentially leading to information disclosure or system compromise.

While the connection to ransomware campaigns remains unknown according to current intelligence, the active exploitation status elevates the risk profile significantly. 

Organizations utilizing affected Citrix NetScaler products face immediate exposure to potential data breaches and system infiltration. 

The vulnerability’s location within the input validation mechanisms makes it particularly concerning, as it could serve as an initial attack vector for more sophisticated multi-stage attacks.

Mitigation 

CISA has established an aggressive remediation timeline, requiring federal agencies to address the vulnerability by July 11, 2025. 

The agency recommends implementing vendor-provided mitigations as the primary response strategy, with specific guidance available through Citrix’s official support documentation.

Organizations are advised to follow applicable guidance under Binding Operational Directive (BOD) 22-01 for cloud services implementations. 

In cases where effective mitigations are unavailable or cannot be implemented promptly, CISA recommends discontinuing use of the affected products until proper security measures can be established.

System administrators should prioritize immediate assessment of their NetScaler deployments and implement appropriate security measures to prevent exploitation of this critical vulnerability.

Investigate live malware behavior, trace every step of an attack, and make faster, smarter security decisions -> Try ANY.RUN now