Raw vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:L/SI:L/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:XSummary
CVE-2025-5777 is a critical-severity Out-of-bounds Read (CWE-125) vulnerability in Citrix Netscaler Application Delivery Controller. Its CVSS base score is 9.3 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique OS Credential Dumping (T1003); ranked in the top 0.0% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SA-15 (Development Process, Standards, and Tools) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2025-5777 is an insufficient input validation flaw that produces a memory overread (CWE-125) on Citrix NetScaler appliances when they are configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, or RDP Proxy) or as an AAA virtual server. The issue also involves use of uninitialized resources (CWE-908, CWE-457). It carries a CVSS 4.0 score of 9.3 and affects the NetScaler data plane when these specific virtual-server roles are active.
Unauthenticated remote attackers can send crafted requests over the network to trigger the overread, enabling them to disclose sensitive memory contents. Successful exploitation can yield session tokens, credentials, or other internal data that facilitate further compromise of the gateway or backend systems.
Citrix addresses the flaw in security bulletin CTX693420, which directs administrators to apply the listed firmware updates for the affected NetScaler versions. Public write-ups from Watchtowr and Horizon3, along with the dedicated citrixbleed.com site, detail the memory-disclosure mechanics and confirm that exploitation has been observed in the wild; CISA has added the CVE to its exploited-vulnerabilities catalog and required federal agencies to patch within one day. The EPSS score rose sharply from a low baseline to a peak of 0.8073 on 2026-02-03 before receding, indicating that active exploitation interest developed after disclosure.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2025-18497
Vulnerability Data
Insufficient input validation leading to memory overread when the NetScaler is configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) OR AAA virtual server
- CWE(s)
- KEV Date Added
- 10 July 2025
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Developer testing and evaluation directly finds out-of-bounds read flaws through static analysis, fuzzing, and dynamic bounds checks.
Requiring documented development standards and tools can mandate initialization checks and safe patterns that stop the weakness from being introduced.
Secure engineering principles require bounds checking and memory-safe constructs that stop out-of-bounds reads from being introduced.
Process isolation confines the effects of an out-of-bounds read to the compromised process.
Input validation rejects malformed indices or lengths that would otherwise cause reads outside buffer bounds.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure-development practices such as bounds checking and memory-safe languages directly prevent out-of-bounds reads.
Vulnerability scanning and recording can discover instances of out-of-bounds reads after code is deployed.
Routine patching replaces vulnerable code containing out-of-bounds read flaws.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing in development and acceptance includes fuzzing and static analysis that detect out-of-bounds read defects before release.
Logging can record evidence of an out-of-bounds read but does not prevent the weakness itself.
Secure development life cycle mandates input validation and bounds checking that directly prevent out-of-bounds reads.
Application security requirements include explicit bounds and memory-safety specifications that mitigate buffer over-reads.
Secure system architecture and engineering principles require memory-safe design patterns and runtime protections against out-of-bounds access.
Secure coding standards explicitly forbid unsafe pointer arithmetic and mandate bounds-checked reads, eliminating CWE-125.