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CVE-2025-6543Memory overflow vulnerability leading to unintended control flow and Denial of Service

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

Exploited in the wild

CISA lists this vulnerability in its Known Exploited Vulnerabilities catalog as Citrix NetScaler ADC and Gateway Buffer Overflow Vulnerability.

Added
30 Jun 2025
Fix due (US federal)
21 Jul 2025
Used by ransomware
Not known

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

ENISA's EU Vulnerability Database lists it as exploited, from CISA's KEV and ENISA's EU KEV, since 30 Jun 2025.

Public exploit

An exploit or proof of concept is public: anyone can try it against an unpatched system. CISA's SSVC rates its exploitation: it is being exploited.

Timeline

  1. ID reserved

    By Citrix

  2. · 2 days later

    Published

  3. · 5 days later

    Added to CISA KEV

    Known exploited in the wild

  4. · 8 months later

    Record updated

Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.

Scores

CVSS scores of CVE-2025-6543, by who scored it
Scored byCVSSScoreVector
CitrixCNA (assigner)4.0Critical9.2CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:L/SI:L/SA:L
NVDNVD · Analyzed4.0Critical9.2CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:L/SI:L/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
EPSS (exploitation in 30 days)
10.4% · top 4.2% of all CVEs (14 Nov 2026)
CISA SSVC
Exploitation: active · Automatable: no · Technical impact: total
Loading the EPSS history…

The list uses the assigner's score when there is one, then CISA's, then NVD's: Critical 9.2.

Affected products

  • NetScaler · ADC

    • affected 14.1 – < 47.46
    • affected 13.1 – < 59.19
    • affected 13.1 FIPS and NDcPP – < 37.236

  • NetScaler · Gateway

    • affected 14.1 – < 47.46
    • affected 13.1 – < 59.19
    • affected 13.1 FIPS and NDcPP – < 37.236

References

References2

Sources

The same CVE in the primary databases and aggregators, to check against.

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Record last updated .