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A new security flaw, “CitrixBleed 2,” is now being actively exploited by cybercriminals. This critical vulnerability, discovered in Citrix’s NetScaler ADC and Gateway systems, shares similarities with the previously infamous CitrixBleed flaw, but with more dangerous consequences. The vulnerability, tracked as CVE-2025-5777, poses a significant threat to organizations that use these systems, as it could allow attackers to maintain undetected access to sensitive data for an extended period.
What is CitrixBleed 2?
CitrixBleed 2, identified as CVE-2025-5777, is a critical security flaw found in Citrix’s NetScaler ADC and Gateway devices. The flaw is an out-of-bounds read issue caused by insufficient input validation, which allows attackers to exploit vulnerabilities within the system. Once compromised, the vulnerability gives unauthorized attackers the ability to steal valid session tokens stored in the memory of internet-facing NetScaler devices. These session tokens are used in persistent application sessions and API calls, which significantly differ from session cookies that are tied to temporary browser sessions.
This vulnerability has been given a CVSS score of 9.3, indicating its severe impact. It mirrors the original CitrixBleed vulnerability (CVE-2023-4966), but introduces a new layer of risk by targeting session tokens, which offer persistent access to the attacker. This means that attackers could maintain control over compromised systems even after the user has ended their browser session, allowing them to stay undetected for much longer.
Signs of Active Exploitation
While there
Hijacked Citrix Web sessions on NetScaler devices where authentication occurs without the user’s knowledge.
Session reuse across multiple IP addresses, suggesting attackers are controlling access points from different locations.
Citrix sessions originating from data center-hosting IP addresses, pointing to the use of consumer VPN services to obfuscate attackers’ origins.
LDAP queries indicative of Active Directory reconnaissance, signaling efforts to map network infrastructure.
Detection of the “ADExplorer64.exe” tool, often associated with malicious activities targeting Active Directory environments.
These activities are significant because they show that attackers are not just gaining initial access, but also performing reconnaissance to further their attack. Unlike traditional session cookies, session tokens used in this exploit can provide persistent access, allowing attackers to operate across multiple systems without being detected.
What Undercode Say:
The emergence of CitrixBleed 2 highlights the growing sophistication of cyber threats targeting enterprise systems. Unlike simple vulnerabilities that might offer short-term access, CitrixBleed 2 allows hackers to establish a more lasting foothold within a network, often remaining undetected for prolonged periods. By targeting session tokens rather than temporary cookies, attackers can maintain control over applications and systems for much longer. This creates an elevated risk for organizations, as even after an employee ends their browser session, malicious actors could continue to exploit the vulnerability across other devices and platforms.
What makes CitrixBleed 2 particularly concerning is the fact that it closely mirrors the original CitrixBleed flaw, which caused widespread damage. However, the ability to exploit session tokens introduces a more dangerous dynamic—attackers can linger within systems, steal sensitive data, or disrupt critical business operations without alerting security teams. Furthermore, the usage of consumer VPN services to mask attacker IP addresses complicates the detection process, giving attackers the freedom to move laterally across a network with relative anonymity.
For businesses relying on
Fact Checker Results:
✅ Verified: The vulnerability CVE-2025-5777 is indeed a critical security flaw found in Citrix’s NetScaler devices, as reported by security researchers.
✅ Verified: Exploitation signs like session hijacking, session reuse across multiple IPs, and Active Directory reconnaissance are being observed.
✅ Verified: Citrix has issued patch updates to mitigate the risk of exploitation.
📊 Prediction:
As cybercriminals continue to target critical infrastructure vulnerabilities, we can expect CitrixBleed 2 to become a focal point for attackers looking to maintain undetected access. This will likely lead to a rise in cyberattack incidents against organizations using Citrix solutions, particularly those that have not yet implemented the latest patches. Over the coming months, more sophisticated techniques could emerge, leveraging the vulnerabilities to breach even more security layers, making early patching and robust network monitoring essential for businesses to stay secure.
References:
Reported By: www.darkreading.com
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