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Exploited vulnerability · CISA KEV

Is CVE-2023-4966 exploited? Yes: in CISA KEV since 18 Oct 2023

Gociux · Citrix NetScaler ADC and NetScaler Gateway · data: CISA KEV, CVE record, FIRST EPSS

Yes. CVE-2023-4966, Citrix NetScaler ADC and NetScaler Gateway Buffer Overflow Vulnerability, is being exploited in the wild. CISA added it to its Known Exploited Vulnerabilities catalog on 18 Oct 2023, 8 days after it was published. It is known to be used in ransomware campaigns. It affects Citrix NetScaler ADC and NetScaler Gateway, an internet-facing product of the kind attackers use for initial access. If you run it, CISA's required action is: Apply mitigations and kill all active and persistent sessions per vendor instructions [https://www.netscaler.com/blog/news/cve-2023-4966-critical-security-update-now-available-for-netscaler-adc-and-netscaler-gateway/] OR discontinue use of the product if mitigations are unavailable.

exploitedYesCISA KEV · 18 Oct 2023
ransomwareKnownused in campaigns
EPSStop 1%among the most likely CVEs to be exploited
severity9.4CVSS 3.1 · critical
US federal due8 Nov 2023BOD 22-01 deadline

What it is

Citrix NetScaler ADC and NetScaler Gateway contain a buffer overflow vulnerability that allows for sensitive information disclosure when configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) or AAA virtual server.

VendorCitrix (27 exploited CVEs in KEV)
ProductNetScaler ADC and NetScaler Gateway
VulnerabilityCitrix NetScaler ADC and NetScaler Gateway Buffer Overflow Vulnerability
WeaknessCWE-119
Published10 Oct 2023
Added to KEV18 Oct 2023
Reported by (CNA)Citrix

What to do

  1. Check whether you run it. Look for NetScaler ADC and NetScaler Gateway in your asset inventory, including appliances and cloud images. Stack check lists every exploited Citrix CVE at once.
  2. Apply the fix. Apply mitigations and kill all active and persistent sessions per vendor instructions [https://www.netscaler.com/blog/news/cve-2023-4966-critical-security-update-now-available-for-netscaler-adc-and-netscaler-gateway/] OR discontinue use of the product if mitigations are unavailable.
  3. If you can't patch today, take the affected service off the internet or restrict who can reach it, and check its logs for signs of compromise since 10 Oct 2023.
  4. Get told next time. Email alerts when CISA adds a CVE for Citrix.

Other exploited CVEs in NetScaler ADC and NetScaler Gateway

References

Questions

Is CVE-2023-4966 being exploited?

Yes. CISA added CVE-2023-4966 to the Known Exploited Vulnerabilities catalog on 18 Oct 2023, which means there is reliable evidence of exploitation in the wild.

Is CVE-2023-4966 used in ransomware attacks?

Yes, CISA lists it as known to be used in ransomware campaigns.

How do I fix CVE-2023-4966?

Apply mitigations and kill all active and persistent sessions per vendor instructions [https://www.netscaler.com/blog/news/cve-2023-4966-critical-security-update-now-available-for-netscaler-adc-and-netscaler-gateway/] OR discontinue use of the product if mitigations are unavailable. Check Citrix's advisory for the fixed versions, and if you can't patch quickly, restrict access to the affected NetScaler ADC and NetScaler Gateway and watch it for signs of compromise.

Sources: CISA KEV (exploitation, ransomware use, required action, due date), the CVE record (publication date, CVSS, CNA), NVD and FIRST EPSS (live score). More: all KEV additions in October 2023 · Citrix scorecard · act-now radar.

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