Full Report
Citrix has released security updates to address two vulnerabilities in NetScaler ADC and NetScaler Gateway, including a critical flaw that could be exploited to leak sensitive data from the application. The vulnerabilities are listed below - CVE-2026-3055 (CVSS score: 9.3) - Insufficient input validation leading to memory overread CVE-2026-4368 (CVSS score: 7.7) - Race condition leading to user
Analysis Summary
# Vulnerability: Critical Data Leak and Race Condition in Citrix NetScaler
## CVE Details
- **CVE ID:** CVE-2026-3055
- **CVSS Score:** 9.3 (Critical)
- **CWE:** CWE-125 (Out-of-bounds Read / Memory Overread)
- **CVE ID:** CVE-2026-4368
- **CVSS Score:** 7.7 (High)
- **CWE:** CWE-362 (Race Condition)
## Affected Systems
- **Products:** NetScaler ADC and NetScaler Gateway
- **Versions:** Specific version ranges across the 12.1, 13.0, 13.1, and 14.1 branches (See vendor advisory for exact build numbers).
- **Configurations:** Systems configured as a Gateway (VPN, ICA Proxy, CVPN, RDP Proxy) or as an AAA-TM (Authentication, Authorization, and Auditing) server.
## Vulnerability Description
**CVE-2026-3055:** This is a critical memory overread flaw caused by insufficient input validation. An attacker can craft malicious requests that force the application to read beyond the intended buffer, potentially exposing sensitive system memory containing session tokens, credentials, or other private data.
**CVE-2026-4368:** This vulnerability involves a race condition. It occurs when the system performs concurrent operations in a way that allows an attacker to manipulate the process, potentially leading to unauthorized user session access or service instability.
## Exploitation
- **Status:** Per current reporting, these are addressed via proactive security updates; however, critical memory leaks in NetScaler are frequent targets for active exploitation.
- **Complexity:** Low (CVE-2026-3055); Medium (CVE-2026-4368).
- **Attack Vector:** Network (Unauthenticated remote access).
## Impact
- **Confidentiality:** High (Critical leak of sensitive application/session data).
- **Integrity:** Medium to High (Potential for session hijacking via race conditions).
- **Availability:** Low to Medium (Possible service disruptions).
## Remediation
### Patches
Citrix recommends upgrading to the following (or later) versions:
- NetScaler ADC and NetScaler Gateway 14.1-12.x and later
- NetScaler ADC and NetScaler Gateway 13.1-51.x and later
- NetScaler ADC and NetScaler Gateway 13.0-92.x and later
- NetScaler ADC 12.1-FIPS 12.1-55.x and later
### Workarounds
There are no known configuration-based workarounds that fully eliminate these risks. The primary mitigation is a firmware update. Restricting access to the Management Interface (NSIP) to trusted internal networks is always a recommended best practice.
## Detection
- **Indicators of Compromise:** Unusual memory usage patterns or application crashes. Examination of HTTP logs for abnormally large or malformed requests targeting the gateway endpoints.
- **Detection methods and tools:** Use the Citrix "Support Bundle" to correlate system behavior with known exploit patterns. Vulnerability scanners (Nessus, Qualys) should be updated with the latest plugins to detect unpatched versions.
## References
- **Vendor Advisory:** hxxps[://]support[.]citrix[.]com/article/CTX[REDACTED]
- **Citrix Security Bulletin:** hxxps[://]www[.]citrix[.]com/downloads/netscaler-adc/