CVE-2026-88771

Hackers Exploit Two Critical Citrix NetScaler Zero-Days to Deploy Web Shells and Enable Lateral Movement

Two critical zero-day vulnerabilities in Citrix NetScaler, tracked as CVE-2026-88771 and CVE-2026-88772, are being actively exploited in the wild to achieve unauthenticated remote code execution. Attackers deploy password-protected PHP web shells such as WHIPSHOT and use the Python-based SLAPSHOT tunneling tool for lateral movement inside targeted networks. The flaws affect NetScaler ADC and NetScaler Gateway appliances with default configurations, and one requires DTLS enabled on VPN vServers. Citrix has released patches for versions 13.1-64.23 and 14.1-73.37, while CISA added the issues to its KEV catalog with a September 30, 2026 remediation deadline for U.S. federal agencies. Organizations are advised to hunt for indicators including modified httpd.conf entries, anomalous setuid permissions on /bin/sh, and suspicious files in /var/netscaler/logon/LogonPoint/custom before applying updates.

CISA Adds Two Critical Citrix NetScaler Flaws to Known Exploited Vulnerabilities Catalog

The CISA has added two critical vulnerabilities affecting Citrix NetScaler ADC and Gateway to its Known Exploited Vulnerabilities catalog following reports of active global exploitation. Both CVE-2026-88771 and CVE-2026-88772 carry a CVSS score of 9.5 and were patched by Citrix on September 27, the same day they were added to the catalog. The first flaw stems from improper input validation and allows unauthenticated arbitrary command execution on default installations. The second issue involves a buffer overflow that can lead to remote code execution or denial of service when DTLS is enabled on VPN virtual servers. Affected versions include 14.1-73.32, 13.1-63.21 and earlier, with fixes available in 14.1-73.37, 13.1-64.23 and later releases including FIPS variants. The issues were identified by watchTowr on September 26, and Citrix confirmed ongoing attacks against unpatched systems. Organizations are advised to apply patches immediately while preserving evidence and following full incident response procedures.

CISA Sets September 30 Deadline for Federal Agencies to Patch Actively Exploited Citrix NetScaler Zero-Days

CISA has ordered U.S. federal agencies to apply patches by September 30 for two actively exploited zero-day vulnerabilities in Citrix NetScaler ADC and NetScaler Gateway. The flaws, tracked as CVE-2026-88771 and CVE-2026-88772, enable unauthenticated remote code execution under default configurations and affect systems commonly exposed to the internet. CVE-2026-88771 allows remote code execution without authentication on NetScaler ADC and Gateway, while CVE-2026-88772 can trigger remote code execution or denial of service via a memory overflow when DTLS is enabled on VPN vServers. Citrix has released fixes for versions 14.1 and 13.1, including FIPS and NDcPP builds, with minimum required builds of 14.1-73.37 and 13.1-64.23. The advisory also covers six additional vulnerabilities from CVE-2026-88773 to CVE-2026-88778 involving HTTP request smuggling and TCP ISN prediction issues. Unsupported branches NetScaler 12.1 and 13.0 receive no patches, requiring immediate migration. Organizations are advised to inventory instances, check for compromise indicators before patching, and preserve forensic evidence.

Multiple Critical Vulnerabilities Found in Citrix NetScaler ADC and Gateway, Two Actively Exploited

Cloud Software Group disclosed eight vulnerabilities affecting NetScaler ADC and NetScaler Gateway products on September 27, 2026. Two of the issues, CVE-2026-88771 and CVE-2026-88772, have already been confirmed as exploited in the wild, prompting urgent remediation advice. CVE-2026-88771 stems from insufficient input validation and allows unauthenticated remote code execution across all default configurations. CVE-2026-88772 involves a memory overflow that can lead to code execution or denial of service when DTLS is enabled, which occurs by default on VPN vServers. The remaining six vulnerabilities cover code execution, denial of service, and HTTP request smuggling risks, with the advisory rated Critical overall. Organizations are urged to apply patches immediately and investigate potential breaches.