Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:LCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2023-4966 is a critical-severity Improper Restriction of Operations within the Bounds of a Memory Buffer (CWE-119) vulnerability in Citrix Netscaler Application Delivery Controller. Its CVSS base score is 9.4 (Critical).
Operationally, ranked in the top 0.0% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog; a public proof-of-concept is referenced.
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-2023-4966 is a sensitive information disclosure vulnerability affecting Citrix NetScaler ADC and NetScaler Gateway appliances when configured as a Gateway (including VPN virtual server, ICA Proxy, CVPN, or RDP Proxy) or as an AAA virtual server. The flaw, tracked under CWE-119, carries a CVSS 3.1 score of 9.4 and permits exposure of sensitive session data without requiring authentication or user interaction.
Unauthenticated remote attackers can exploit the issue over the network to leak session tokens and other sensitive information, enabling session hijacking and subsequent unauthorized access with impacts to confidentiality, integrity, and availability. Public proof-of-concept code has been released that demonstrates token leakage against vulnerable instances.
Citrix advisory CTX579459 details the affected versions and provides remediation guidance, while CISA has added the CVE to its Known Exploited Vulnerabilities catalog, confirming in-the-wild exploitation. The associated EPSS score has reached a peak of 0.9717 with a current value of 0.9435, indicating sustained and substantial exploitation interest following disclosure.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2023-54802
Vulnerability Data
Sensitive information disclosure in NetScaler ADC and NetScaler Gateway when configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) or AAA virtual server.
- CWE(s)
- KEV Date Added
- 18 October 2023
Related Threats
Threat-Actor AttributionAI
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Affected Assets
Mitigating Controls
Likely Mitigating Controls AI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Ongoing control assessments and code testing (static/dynamic analysis, fuzzing) surface memory buffer restriction failures, which are then remediated before release.
Managed runtimes used by platform-independent applications (e.g., JVM, CLR) enforce memory safety, preventing most buffer overflows that require direct memory manipulation.
Memory protections (e.g., W^X, ASLR) make exploitation of buffer-boundary violations far harder to turn into code execution.
Detects exploitation attempts that produce memory corruption, crashes, or anomalous behavior.
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.
A.8.25 mandates secure SDLC practices (secure coding guidelines, security requirements, testing including code scans and penetration tests, developer training) that reach buffer management and can stop many buffer overruns from reaching production, but leaves a bounded remainder (e.g. flaws in non-software components, incomplete enforcement of guidelines, or post-deployment changes)
Application security requirements can specify memory-safety rules, but do not prescribe implementation details.
A.8.27 mandates security-by-design principles (e.g. least privilege, fail securely, distrust external input, hardening) plus design reviews that can catch and stop buffer-boundary errors before they reach code, but this is only one minority slice of CWE-119's broad surface (language-specific flaws, unsafe library use, compiler/runtime mitigations, and post-deployment instances remain outside its direct scope).
Secure coding standards explicitly forbid unsafe buffer operations, directly eliminating CWE-119.
Security testing in development catches out-of-bounds accesses before release, covering most instances of the weakness.
Hardening callouts derived
DISA STIG baselines are authored against specific weaknesses. Where this CVE cites a broad weakness class, the mapping is not asserted at that abstraction (owner ruling, 2026-09-25: grade only at Base and below), so no rule is shown here rather than a rule shown against the wrong grain.
- No fine-grained STIG row for CWE-119, a class-level weakness. Rules are authored against its narrower children: CWE-823.