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CVE-2023-6549

Exploitation: active CVSS 8.2 HIGH

CVSS base score: 8.2 (High) vendor CNA · v3.1

Score assigned by the vendor's own CVE Numbering Authority (CNA); CISA's Vulnrichment program adds a score only when the CNA omits one.

Citrix NetScaler ADC and NetScaler Gateway Buffer Overflow Vulnerability

Vendor: Citrix   Product: NetScaler ADC and NetScaler Gateway

Description

Citrix NetScaler ADC and NetScaler Gateway contain a buffer overflow vulnerability that allows for a denial-of-service when configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) or AAA virtual server.

Lifecycle Timeline

Each milestone comes from a different source, so gaps between them are gaps in what those sources publish, not evidence that nothing happened. EPSS history for this CVE holds 151 points from 2024-01-27, tracked daily from 2026-09-09; earlier points are weekly, which dates a spike to within a week. Peak probability 84.5% on 2025-10-18.

Published Applicability

CVE List v5 (CNA container) 6 affected · 0 fixed · 0 not affected

Check whether a specific version is affected →

What each source publishes about which product versions carry this vulnerability, kept as written rather than merged. Absence here means no source has published applicability data, not that nothing is affected.

Research & News Coverage

No mentions found in monitored research blogs or news feeds.

Detection & Exploitation

Scan
Exploit / Pen Test
none published
Host / SIEM
none published

Coverage across public collections only: Nuclei and OpenVAS NVT (scan); Snort and Suricata ET Open (network); Sigma and YARA (host/SIEM); Metasploit, Exploit-DB and public GitHub repositories (exploit). Absence here means nothing public was found, not that detection is impossible.
GitHub PoC repositories are collected automatically by PoC-in-GitHub (CC0) and are not vetted: some are fakes and some are malware. Treat them as evidence that code was published, not as code to run.
OpenVAS coverage derives from the Greenbone Community Feed, made available under the Open Database License (ODbL) v1.0; its individual Vulnerability Tests are licensed GNU GPL v2.

CISA Assessment (Vulnrichment / SSVC)

active
yes
partial
—
8.2 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
CWE-119 — Improper Restriction of Operations within the Bounds of a Memory Buffer
2025-02-03

D3FEND Countermeasures

Defensive techniques inferred by MITRE D3FEND from the underlying weakness (CWE-119) — general hardening and detection guidance for this weakness class, not a vendor patch for this specific CVE.

KEV Catalog Status

2024-01-17
2024-02-07
Unknown

Listed By

SourceDateRecord
CISA KEV 2024-01-17 source record →
CISA Vulnrichment 2025-02-03 source record →

Referenced in Advisories

DateAdvisoryIssuer
2025-02-12 Secure by Design Alert: Eliminating Buffer Overflow Vulnerabilities FBI
2024-07-18 2024-010: Vulnerabilities in Netscaler ADS and Netscaler Gateway CERT-EU
2024-01-18 Citrix Releases Security Updates for NetScaler ADC and NetScaler Gateway CISA

Weaponization Timeline — Offensive & Testing Tools

No exploit-tool sightings recorded for this CVE.

Evidence tiers are explained on the About page — a merged Metasploit module is far stronger evidence than a distro package mention.

External References