CVE-2025-6543 (GCVE-0-2025-6543)

Vulnerability from cvelistv5 – Published: 2025-06-25 12:49 – Updated: 2026-02-26 17:50
VLAI CISA ENISA Shadowserver Previdian
Title
Memory overflow vulnerability leading to unintended control flow and Denial of Service
Summary
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
Severity
9.2 (Critical)
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:L/SI:L/SA:L
SSVC
Exploitation: active Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2025-07-17 03:55 UTC
CWE
  • CWE-119 - Improper Restriction of Operations within the Bounds of a Memory Buffer
Assigner
Citrix CNA under the mitre root
CNA scorecard C 66/100 over 10 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
NetScaler ADC Affected: 14.1 , < 47.46 (patch)
Affected: 13.1 , < 59.19 (patch)
Affected: 13.1 FIPS and NDcPP , < 37.236 (patch)
guessed Create a notification for this product.
NetScaler Gateway Affected: 14.1 , < 47.46 (patch)
Affected: 13.1 , < 59.19 (patch)
Affected: 13.1 FIPS and NDcPP , < 37.236 (patch)
guessed Create a notification for this product.
Date Public
2025-06-25 12:30
CISA
Known Exploited Vulnerability - GCVE BCP-07 Compliant
KEV entry ID: 55baa5cc-0875-463e-ab0f-9b3d985ffade

Vulnerability ID: CVE-2025-6543

Status: Confirmed

Status Updated: 2025-06-30 00:00 UTC

Exploited: Yes

Timestamps
First Seen: 2025-06-30
Asserted: 2025-06-30
Scope
Notes: Citrix NetScaler ADC and Gateway Buffer Overflow Vulnerability | Affected: Citrix / NetScaler ADC and Gateway | Description: 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. | Required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. | Due date: 2025-07-21 | Known ransomware campaign use (KEV): Unknown | Notes (KEV): 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
Evidence

Type: Vendor Report

Signal: Successful Exploitation

Confidence: 80%

Source: cisa-kev

Details
Cwes CWE-119
Feed CISA Known Exploited Vulnerabilities Catalog
Product NetScaler ADC and Gateway
Due Date 2025-07-21
Date Added 2025-06-30
Vendorproject Citrix
Vulnerabilityname Citrix NetScaler ADC and Gateway Buffer Overflow Vulnerability
Knownransomwarecampaignuse Unknown
References
Created: 2026-02-02 12:25 UTC | Updated: 2026-11-04 13:37 UTC
ENISA
Known Exploited Vulnerability - GCVE BCP-07 Compliant
KEV entry ID: b9f8f3b7-d580-4894-a55a-6a0afcfb366f

Vulnerability ID: CVE-2025-6543

Status: Confirmed

Status Updated: 2025-07-18 00:00 UTC

Exploited: Yes

Timestamps
First Seen: 2025-07-18
Asserted: 2025-07-18
Scope
Notes: Affected: Citrix / NetScaler ADC and NetScaler Gateway | Description: 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. | Patched since: 2025/06/25 | Exploitation type: unknown | Origin source: CNW
Evidence

Type: Csirt Report

Signal: Successful Exploitation

Confidence: 75%

Source: enisa-cnw-kev

Details
Cwes
Euvd EUVD-2025-19085
Notes
Catalog ENISA / EU CSIRTs Network (CNW) KEV JSON
Product NetScaler ADC and NetScaler Gateway
Datereported 2025/07/18
Originsource CNW
Patchedsince 2025/06/25
Vendorproject Citrix
Exploitationtype unknown
Vulnerabilityname
Threatactorsexploiting
References
Created: 2026-02-02 12:25 UTC | Updated: 2026-11-04 13:28 UTC
Shadowserver
Known Exploited Vulnerability - GCVE BCP-07 Compliant
KEV entry ID: f3dd3369-2790-4b4d-ae51-7347041acfcf

Vulnerability ID: CVE-2025-6543

Status: Confirmed

Status Updated: 2025-07-30 08:58 UTC

Exploited: Yes

Characteristics
Severity: 0.0
Timestamps
First Seen: 2025-07-30
Asserted: 2025-07-30
Last Seen: 2025-07-30
Scope
Asset Exposure: ['internet-facing']
Notes: Affected: Citrix / Citrix NetScaler ADC and NetScaler Gateway | Class: app-delivery-controller | Severity: None (CVSS 0) | IoT: no | In CISA KEV: yes | Honeypot connections on 2025-07-30: 14
Evidence

Type: Honeypot

Signal: In The Wild Attempts

Confidence: 70%

Source: shadowserver

Details
1D 1
Iot no
Feed Shadowserver Foundation honeypot/exploited-vulnerabilities
Type http-scan
Class app-delivery-controller
7D Avg 0
Vendor Citrix
30D Avg 0
90D Avg 0
Product Citrix NetScaler ADC and NetScaler Gateway
Cisa Kev yes
Connections 14
Observation Date 2025-07-30
Vulnerability Class CVSS
Vulnerability Score 0
Vulnerability Severity None
References
Created: 2026-06-30 10:22 UTC | Updated: 2026-06-30 11:39 UTC
Previdian
Known Exploited Vulnerability - GCVE BCP-07 Compliant
KEV entry ID: 8e6243a3-164a-429f-a8d0-9a27f129b335

Vulnerability ID: CVE-2025-6543

Status: Confirmed

Status Updated: 2026-06-01 10:36 UTC

Exploited: Yes

Timestamps
First Seen: 2026-06-01
Asserted: 2026-06-01
Scope
Notes: KEVIntel entry: Memory overflow vulnerability leading to unintended control flow and Denial of Service | Affected: NetScaler / ADC, Gateway | CVSS: 9.2 (CRITICAL) | EPSS: 0.09756 | Used in malware: unknown | Not yet in CISA KEV: False
Evidence

Type: Public Report

Signal: Successful Exploitation

Confidence: 70%

Source: kevintel

Details
Feed KEVIntel (kevintel.com)
Title Memory overflow vulnerability leading to unintended control flow and Denial of Service
Vendor NetScaler
Product ADC, Gateway
Added Date 2026-06-01T10:36:14.774Z
Cvss Score 9.2
Epss Score 0.09756
Cvss Severity CRITICAL
Epss Percentile 0.94917
Used In Malware unknown
Ahead Of Cisa Kev 
{
  "count": 1,
  "unit": "day"
}
Not Yet In Cisa Kev False
References
Created: 2026-06-23 14:03 UTC | Updated: 2026-07-10 06:14 UTC
Show details on NVD website
To clipboard 

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}



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Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.

Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

JSON
How durations are calculated

Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.

Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.

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    Related by attack behaviour

    Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.