Possible Citrix NetScaler Webshell Deployment under VPN Theme Directory (CVE-2023-3519) (via webserver)

ATT&CK techniques

Persistence

Recon
Resource Dev
Initial Access
Execution
Persistence
- T1505.003Web Shell
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule detects requests to PHP files located under the NetScaler VPN theme directory. This maps to post-exploitation of CVE-2023-3519 where attackers write a PHP webshell to /var/vpn/theme after the buffer overflow. Access to a PHP resource in this static theme path indicates a deployed webshell used for persistent remote command execution.

Reporting behind it

Related detections9 linkedT1505.003 — drag to rearrange

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Possible Citrix NetScaler Webshell Deployment under VPN Theme Directory (CVE-2023-3519) (via webserver)

Pivot detection · T1505.003 · 9 related

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

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