CVE-2025-6543
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
do firstApply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Can a WAF block it? No. The vulnerability occurs in Citrix NetScaler ADC and Gateway when configured as VPN or AAA servers, which handle non-HTTP protocols like ICA, CVPN, or RDP proxy. The attack uses these protocols rather than HTTP requests, so a web application firewall cannot filter the malicious input.
Also consider: patch
Based on an AI reading of the CVE description, and no vendor rule found yet. We check Cloudflare, AWS, Google Cloud Armor and Azure; for Akamai, Imperva, Fastly, F5, ask your vendor.
Is CVE-2025-6543 being exploited?
Yes. CVE-2025-6543 appears in CISA's Known Exploited Vulnerabilities catalog, which means exploitation in the wild has been confirmed and reported. Treat it as active rather than theoretical, and patch it ahead of higher-scoring vulnerabilities that carry no exploitation evidence.
How severe is CVE-2025-6543?
CVE-2025-6543 is rated Critical with a CVSS score of 9.8. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2025-6543?
Yes. A fix has been recorded for CVE-2025-6543. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2025-6543 affect?
CVE-2025-6543 affects citrix:netscaler_application_delivery_controller, citrix:netscaler_gateway. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
- affected>= 14.1 and < 47.46
- affected>= 13.1 and < 59.19
- affected>= 13.1 FIPS and NDcPP and < 37.236
- affected>= 14.1 and < 47.46
- affected>= 13.1 and < 59.19
- affected>= 13.1 FIPS and NDcPP and < 37.236
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.
public exploits
Unvetted proof-of-concept code on GitHub: 3 GitHub proofs of concept
Listed so you can judge urgency, not as a recommendation to run anything. GitHub “proofs of concept” are unvetted: some are fake or carry malware. Exploit-DB marks the entries its staff verified.
cisa ssvc
- exploitation
- active
- automatable
- no
- technical impact
- total
Assessed by CISA 17 Jul 2025 (SSVC 2.0.3).
timeline
- 25 Jun 2025Published
- 26 Jun 2025First proof-of-concept repository on GitHub (unvetted) · same day later
- 30 Jun 2025Added to CISA KEV (exploited in the wild) · 4 days later
- 17 Jul 2025CISA SSVC assessment: exploitation active · 17 days later
- 21 Jul 2025CISA remediation due date (US federal agencies) · 4 days later
- 26 Feb 2026CVE record last updated · 221 days (about 7 months) later
- 2 Nov 2026Analysed by vulneraibility.com · 249 days (about 8 months) later
- Linksupport.citrix.com /support-home/kbsearch/article?articleNumber=CTX694788
- Linkcisa.gov /known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-6543
sources
- CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
- NVD: CVSS and CPE data
- CISA KEV catalog: exploitation, date added, due date
- CISA Vulnrichment (ADP): SSVC decision points
- FIRST EPSS: exploit probability and percentile
- PoC-in-GitHub: GitHub repositories that claim a proof of concept
- Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.