CVE-2023-6549: Citrix NetScaler ADC and NetScaler Gateway Buffer Overflow Vulnerability
- Is it exploited?
Yes. CISA added it to the Known Exploited Vulnerabilities catalog on 17 Jan 2024, the same day the CVE record was published.
- How likely is exploitation in the next 30 days?
- 57.6%
EPSS score, percentile 99.1 of all scored records
- How severe?
- 8.2 High
CVSS v3.1 base score, given by the CNA
- What should I do?
Required action (CISA), due 7 Feb 2024: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
The CVE record links no vendor advisory, patch or mitigation.
- Which versions are affected?
Affected: 14.1 up to, not including, 12.35; 13.1 up to, not including, 51.15; 13.0 up to, not including, 92.21; 13.1-FIPS up to, not including, 37.176; 12.1-FIPS up to, not including, 55.302; 12.1-NDcPP up to, not including, 55.302
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
What to do
Required action, set by CISA
Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
CISA due date for this action: 7 February 2024.
Advisories and patches
The CVE record links no vendor advisory, patch or mitigation.
Linked from CISA's catalog entry
- https://support.citrix.com/article/CTX584986/netscaler-adc-and-netscaler-gateway-security-bulletin-for-cve20236548-and-cve20236549
- https://nvd.nist.gov/vuln/detail/CVE-2023-6549
Affected products and versions
As listed in the CVE record.
| Status | Versions |
|---|---|
| Affected | 14.1 up to, not including, 12.35 |
| Affected | 13.1 up to, not including, 51.15 |
| Affected | 13.0 up to, not including, 92.21 |
| Affected | 13.1-FIPS up to, not including, 37.176 |
| Affected | 12.1-FIPS up to, not including, 55.302 |
| Affected | 12.1-NDcPP up to, not including, 55.302 |
Versions not listed are: unaffected.
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
About this vulnerability
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.
Summary: CISA's KEV catalog, as of 28 Oct 2026.
- CISA added CVE-2023-6549 to its Known Exploited Vulnerabilities (KEV) catalog on 17 Jan 2024.
- CISA's ransomware flag for this entry is "Unknown": no evidence of ransomware use in the catalog, which is not proof of none.
- The due date CISA sets for the required action is 7 Feb 2024.
- The CVE record was published on 17 Jan 2024, the same day it was added to KEV.
- The CVE record carries a CVSS v3.1 base score of 8.2 (High), given by its CNA.
- FIRST's EPSS model puts the probability of exploitation in the next 30 days at 57.6% (percentile 99.1), as of 28 Oct 2026.
- CISA's SSVC assessment in the CVE record: exploitation active, automatable yes, technical impact partial.
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026. About the data.
Description
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
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
Weakness
- CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer
CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record and the KEV entry.
Timeline
| Date | Event |
|---|---|
| 17 Jan 2024 | CVE record published |
| 17 Jan 2024 | Added to CISA KEV |
| 7 Feb 2024 | CISA due date for the required action |
| 21 Oct 2025 | CVE record last updated |
References
More exploited Citrix vulnerabilities
- CVE-2026-88779: Citrix NetScaler Improper Restriction of Operations within the Bounds of a Memory Buffer Vulnerability
- CVE-2026-88771: Citrix NetScaler Improper Input Validation Vulnerability
- CVE-2026-88772: Citrix NetScaler Improper Restriction of Operations within the Bounds of a Memory Buffer Vulnerability
- CVE-2026-19490: Citrix NetScaler Authentication Bypass Using an Alternate Path or Channel Vulnerability
- CVE-2026-8452: Citrix NetScaler ADC and NetScaler Gateway Improper Restriction of Operations within the Bounds of a Memory Buffer Vulnerability
- CVE-2026-3055: Citrix NetScaler Out-of-Bounds Read Vulnerability