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Multiple severe vulnerabilities in Citrix ADC and NetScaler Gateway exposed organizations to unauthenticated compromise, including remote code execution in CVE-2019-19781 and CVE-2023-3519, as well as memory disclosure in CVE-2023-4966 (CitrixBleed) and the later CVE-2025-5777 variant. Public reporting showed that CVE-2019-19781 could be exploited through crafted HTTP requests that abused directory traversal and template parsing to execute commands on vulnerable appliances, while research on CVE-2023-3519 examined another critical path to code execution on internet-facing Citrix infrastructure.
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14 events from the most recent confirmed update back to the earliest known activity.
Cybersecurity Dive reported that Citrix NetScaler products were confirmed to be under exploitation. This represents a new public confirmation of active abuse affecting NetScaler systems beyond the previously documented 2025 CitrixBleed 2 reporting.
Akamai published mitigation guidance for CVE-2025-5777, referred to as CitrixBleed 2, affecting NetScaler memory disclosure. The publication reflects public technical guidance on defending against the flaw.
Reporting indicated that CVE-2025-5777, dubbed CitrixBleed 2, was already being exploited in the wild while many organizations were slow to patch affected NetScaler systems. The development marked an escalation from vulnerability awareness to observed malicious abuse.
Computer Weekly reported that CVE-2025-5777, known as CitrixBleed 2, was believed to be under active attack. This marks public reporting that the vulnerability had moved from disclosure concern to suspected in-the-wild exploitation.
Citrix published a NetScaler ADC and NetScaler Gateway security bulletin covering CVE-2025-5349 and CVE-2025-5777. The advisory marked the vendor's official disclosure and guidance for the vulnerabilities affecting NetScaler products.
The U.S. Department of Health and Human Services warned the healthcare sector about CitrixBleed attacks after hospital outages were reported. The alert marked a sector-specific government response highlighting operational impact on healthcare organizations.
CISA said the CitrixBleed vulnerability, CVE-2023-4966, was being actively exploited by both nation-state and financially motivated threat actors. The warning marked an official U.S. government alert highlighting the breadth and seriousness of ongoing exploitation.
Following public reporting on CitrixBleed (CVE-2023-4966), defenders were urged to rapidly patch affected NetScaler systems and investigate for signs of compromise as concern grew over active malicious exploitation. The development marked an operational response phase beyond the initial technical reporting on the flaw.
Unit 42 published a threat brief on CVE-2023-4966, commonly known as CitrixBleed, documenting the vulnerability and associated threat activity. This marks public reporting on the issue by early November 2023.
Cloud Software Group disclosed and released fixed builds for CVE-2023-3519, a critical unauthenticated remote code execution flaw affecting customer-managed NetScaler ADC and NetScaler Gateway deployments configured as a gateway or AAA virtual server. The company said no workaround was available beyond upgrading and warned the vulnerability was being exploited in targeted attacks.
Assetnote published research analyzing CVE-2023-3519 in Citrix ADC and NetScaler Gateway, adding technical detail to understanding of the vulnerability. The reference indicates public disclosure of analysis by July 2023.
Citrix released patches for CVE-2019-19781 in late January 2020 after initially providing only mitigation guidance. The fixes addressed the widely exploited remote code execution risk on vulnerable appliances.
By early 2020, public exploit code for CVE-2019-19781 became available and FireEye reported threat actors were actively exploiting vulnerable Citrix systems to install malware, including NOTROBIN. The exploitation chain involved directory traversal and template parsing to achieve unauthenticated remote code execution.
Citrix disclosed the authentication bypass vulnerability CVE-2019-19781 affecting Citrix ADC, Gateway, NetScaler, and SD-WAN WANOP products. The company initially advised customers to apply mitigations before patches were available.
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Citrix NetScaler ADC and NetScaler Gateway appliances are affected by multiple critical vulnerabilities that can expose organizations to compromise, including `CVE-2025-5349`, `CVE-2025-5777`, and `CVE-2026-3055`. The flaws impact supported NetScaler releases, while end-of-life versions `12.1` and `13.0` remain vulnerable without fixes. `CVE-2025-5349` enables access-control bypass on the management interface, `CVE-2025-5777` is an out-of-bounds read that can leak sensitive memory contents, and `CVE-2026-3055` is an input-validation flaw that can lead to memory overwrite when NetScaler is configured as a SAML Identity Provider.
Jun 29, 2026
Citrix released security updates to address multiple vulnerabilities affecting **Citrix XenServer**, **NetScaler ADC**, and **NetScaler Gateway**, warning that the flaws could lead to denial-of-service conditions, memory corruption, disclosure of sensitive information, arbitrary code execution, and unauthorized access. The update was highlighted by EG-FinCIRT, which said organizations should apply the fixes after completing testing. The most prominent issues are **`CVE-2026-8451`** and **`CVE-2026-8452`**, both affecting NetScaler ADC and NetScaler Gateway and each assigned a **CVSS 4.0 score of 8.8**. EG-FinCIRT described `CVE-2026-8451` as an insufficient input validation flaw and `CVE-2026-8452` as a race condition vulnerability, underscoring the risk to internet-facing Citrix infrastructure commonly used for application delivery and remote access.
Jul 14, 2026
Citrix disclosed **CVE-2025-5777** in NetScaler ADC and NetScaler Gateway alongside **CVE-2025-5349**, warning that affected appliances could be exposed to remote exploitation. Public tracking by ENISA’s EUVD and subsequent reporting identified `CVE-2025-5777` as **CitrixBleed 2**, linking the issue to session exposure risks on internet-facing NetScaler deployments and raising concern for organizations that rely on the products for remote access. After the advisory, proof-of-concept and scanning tools for `CVE-2025-5777` appeared on GitHub, including repositories explicitly branded as **CitrixBleed 2** scanners. The rapid publication of exploit-related code lowered the barrier for attackers to identify vulnerable devices, increasing urgency for defenders to patch NetScaler systems, review exposed gateways, and monitor for signs of session theft or unauthorized access.
Jul 3, 2026