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Exploited vulnerability · CISA KEV

Is CVE-2023-6549 exploited? Yes: in CISA KEV since 17 Jan 2024

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

Yes. CVE-2023-6549, 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 17 Jan 2024, the day it was published. 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 per vendor instructions or discontinue use of the product if mitigations are unavailable.

exploitedYesCISA KEV · 17 Jan 2024
ransomwareNot knownno confirmed use
EPSStop 1%among the most likely CVEs to be exploited
severity8.2CVSS 3.1 · high
US federal due7 Feb 2024BOD 22-01 deadline

What it is

Citrix NetScaler ADC and NetScaler Gateway contain a buffer overflow vulnerability that allows for a denial-of-service 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
Published17 Jan 2024
Added to KEV17 Jan 2024
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 per vendor instructions 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 17 Jan 2024.
  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-2023-6549 being exploited?

Yes. CISA added CVE-2023-6549 to the Known Exploited Vulnerabilities catalog on 17 Jan 2024, which means there is reliable evidence of exploitation in the wild.

Is CVE-2023-6549 used in ransomware attacks?

CISA does not list known ransomware use for it. That can change, and exploitation alone is reason to fix it first.

How do I fix CVE-2023-6549?

Apply mitigations per vendor instructions 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 January 2024 · Citrix scorecard · act-now radar.

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