Citrix NetScaler DoS flaw exploited in wild
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CISA reports active exploitation of a remote denial-of-service vulnerability in Citrix NetScaler ADC and Gateway; patches available.
CERT-FR has issued an advisory regarding CVE-2026-88779, a vulnerability affecting Citrix NetScaler ADC and NetScaler Gateway that allows a remote attacker to cause a denial of service. CISA has indicated that this vulnerability is being actively exploited in the wild, raising the urgency for affected organizations to patch promptly.
The vulnerability affects multiple versions of NetScaler ADC (including FIPS variants) and NetScaler Gateway prior to specific patched builds: 13.1-NDcPP 13.1-37.282, 13.1-64.28, 14.1-73.41 FIPS, and 14.1-73.41. Citrix has released a security bulletin (CTX697174) dated October 4, 2026, detailing the fix. Defenders running affected NetScaler deployments should prioritize upgrading to the patched versions given the confirmed active exploitation, as these appliances are commonly internet-facing and denial-of-service against them can disrupt critical VPN and application delivery services.
No further technical details, indicators of compromise, or threat actor attribution were provided in this advisory. Organizations should consult the Citrix bulletin for patching guidance and monitor NetScaler systems for signs of service disruption or crash loops that could indicate exploitation attempts.
Mentioned in this report
Source reporting: https://www.cert.ssi.gouv.fr/avis/CERTFR-2026-AVI-1263
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