CVE-2025-6543: Citrix NetScaler ADC and Gateway Buffer Overflow Vulnerability
- Is it exploited?
Yes. CISA added it to the Known Exploited Vulnerabilities catalog on , 5 days after the CVE record was published.
- How likely is exploitation in the next 30 days?
- 10.4%
EPSS score, percentile 95.7 of all scored records
- How severe?
- 9.2 Critical
CVSS v4.0 base score, given by the CNA
- What should I do?
CISA deadline . Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, 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
- from 14.1 to before 47.46
- from 13.1 to before 59.19
- from 13.1 FIPS and NDcPP to before 37.236
- from 14.1 to before 47.46
- from 13.1 to before 59.19
- from 13.1 FIPS and NDcPP to before 37.236
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of ; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of ; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of . About the data.
What to do
Required action, set by CISA
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
CISA due date for this action: .
Advisories and patches
The CVE record links no vendor advisory, patch or mitigation.
Linked from CISA's catalog entry
- https://support.citrix.com/support-home/kbsearch/article?articleNumber=CTX694788
- https://www.netscaler.com/blog/news/netscaler-critical-security-updates-for-cve-2025-6543-and-cve-2025-5777/
- https://nvd.nist.gov/vuln/detail/CVE-2025-6543
Affected products and versions
As listed in the CVE record.
| Status | Versions |
|---|---|
| Affected | from 14.1 to before 47.46 |
| Affected | from 13.1 to before 59.19 |
| Affected | from 13.1 FIPS and NDcPP to before 37.236 |
Versions not listed are: unaffected.
| Status | Versions |
|---|---|
| Affected | from 14.1 to before 47.46 |
| Affected | from 13.1 to before 59.19 |
| Affected | from 13.1 FIPS and NDcPP to before 37.236 |
Versions not listed are: unaffected.
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of . About the data.
About this vulnerability
Citrix NetScaler ADC and Gateway contain a buffer overflow vulnerability leading to unintended control flow and Denial of Service. NetScaler must be configured as Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) OR AAA virtual server.
Summary: CISA's KEV catalog, as of .
- CISA added CVE-2025-6543 to its Known Exploited Vulnerabilities (KEV) catalog on 30 Jun 2025.
- 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 21 Jul 2025.
- The CVE record was published on 25 Jun 2025, 5 days before it was added to KEV.
- The CVE record carries a CVSS v4.0 base score of 9.2 (Critical), given by its CNA.
- FIRST's EPSS model puts the probability of exploitation in the next 30 days at 10.4% (percentile 95.7), as of 28 Oct 2026.
- CISA's SSVC assessment in the CVE record: exploitation active, automatable no, technical impact total.
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of ; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of ; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of . About the data.
Description
Memory overflow vulnerability leading to unintended control flow and Denial of Service
Memory overflow vulnerability leading to unintended control flow and Denial of Service in NetScaler ADC and NetScaler Gateway when configured as Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) OR AAA virtual server
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of . 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 |
|---|---|
| CVE record published | |
| Added to CISA KEV | |
| CISA due date for the required action | |
| 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