CVE-2023-6549
Memory Safety in Citrix Netscaler Application Delivery Controller 12.1 – 12.1-55.302
Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:HCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2023-6549 is a high-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 8.2 (High).
Operationally, ranked in the top 0.9% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog.
The strongest mitigations our analysis identified map to SA-8 (Security and Privacy Engineering Principles) and SI-10 (Information Input Validation) — 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-2023-6549 is an improper restriction of operations within the bounds of a memory buffer, tracked as CWE-119, that affects NetScaler ADC and NetScaler Gateway. The flaw permits an unauthenticated remote attacker to trigger a denial of service and perform an out-of-bounds memory read, reflected in its CVSS 3.1 score of 8.2 with network attack vector, low complexity, and no required privileges or user interaction.
An unauthenticated attacker with network access can send crafted requests that exploit the memory-handling defect, resulting in service disruption and limited information disclosure through the out-of-bounds read. No authentication or user interaction is needed, enabling remote exploitation against exposed appliances.
Citrix has published security bulletin CTX584986 that addresses both CVE-2023-6548 and CVE-2023-6549, and the vulnerability appears in the CISA Known Exploited Vulnerabilities catalog, indicating confirmed in-the-wild exploitation and the need for prompt remediation through the vendor-supplied updates.
The associated EPSS score stands at 0.8024 with an identical peak value, indicating sustained exploitation interest since disclosure.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2023-58779
Vulnerability Data
Improper Restriction of Operations within the Bounds of a Memory Buffer in NetScaler ADC and NetScaler Gateway allows Unauthenticated Denial of Service and Out-Of-Bounds Memory Read
- CWE(s)
- KEV Date Added
- 17 January 2024
Related Threats
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Secure engineering principles require memory-safe design and coding that structurally avoids buffer-boundary violations.
Input validation directly enforces bounds checking that stops out-of-bounds reads/writes from being introduced or reached.
Memory protection restricts exploitation impact of buffer overflows without eliminating the underlying coding flaw.
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.