Citrix NetScaler Flaws Expose ADC and Gateway to Remote DoS and Memory Errors
Citrix published a security advisory for NetScaler ADC and NetScaler Gateway, warning that multiple high-severity vulnerabilities can be exploited remotely in specific deployments and configurations. The advisory, highlighted by the Canadian Centre for Cyber Security, affects the 14.1 and 13.1 release lines as well as certain NetScaler FIPS and NDcPP editions, and references six CVEs including CVE-2026-8451, CVE-2026-8452, CVE-2026-8655, and CVE-2026-13474. Administrators were urged to review Citrix’s bulletin and move affected systems to fixed versions.
The disclosed flaws include a malformed HTTP/2 request issue that can trigger denial of service when HTTP/2 is enabled on affected LB, CS, VPN virtual servers or services (CVE-2026-13474); multiple memory overflow vulnerabilities tied to Oracle load balancer, DNS proxy, and DNS recursive resolver deployments (CVE-2026-8655); a memory overread caused by insufficient input validation when NetScaler is configured as a SAML Identity Provider (CVE-2026-8451); and a separate memory overflow vulnerability affecting Gateway or AAA virtual servers, including SSL VPN, ICA Proxy, CVPN, and RDP Proxy deployments (CVE-2026-8452). Recommended mitigations include applying Citrix security updates, disabling HTTP/2 or vulnerable Gateway features where not required, reviewing exposed virtual server and HTTP profile configurations, and monitoring for anomalous behavior.
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How this story unfolded
7 events from the most recent confirmed update back to the earliest known activity.
Canadian Cyber Centre urges NetScaler administrators to update
On 2026-06-30, the Canadian Centre for Cyber Security published alert AV26-645 highlighting Citrix's NetScaler advisory and urging users and administrators to review the bulletin and apply the necessary updates. It noted that affected products remain vulnerable until updated to the fixed versions.
Citrix adds manual mitigation guidance for CVE-2026-13474
Citrix said some deployments affected by CVE-2026-13474 require not only upgrading to fixed NetScaler versions but also manually configuring Http2SmallWndTimeout to fully address the HTTP/2 denial-of-service issue. The company also stated it had no evidence of in-the-wild exploitation at the time of disclosure.
CVE-2026-13474 disclosed for malformed HTTP/2 request DoS
CVE-2026-13474 was disclosed as a high-severity denial-of-service vulnerability affecting NetScaler ADC and NetScaler Gateway when HTTP/2 is enabled in an HTTP Profile tied to certain virtual servers or services. The issue can be triggered remotely through malformed HTTP/2 requests.
CVE-2026-8655 disclosed for Oracle and DNS NetScaler roles
CVE-2026-8655 was disclosed as multiple memory overflow vulnerabilities in NetScaler ADC and NetScaler Gateway that can lead to erroneous behavior and denial of service. Exploitation is possible when NetScaler ADC is configured as an Oracle load balancer, DNS proxy, or DNS recursive resolver.
CVE-2026-8452 disclosed for NetScaler Gateway and AAA servers
CVE-2026-8452 was disclosed as a high-severity memory overflow vulnerability in NetScaler ADC and NetScaler Gateway affecting Gateway or AAA virtual server deployments, including SSL VPN, ICA Proxy, CVPN, and RDP Proxy. The flaw can cause unpredictable behavior or denial of service and is described as remotely exploitable.
CVE-2026-8451 disclosed for NetScaler SAML IDP deployments
CVE-2026-8451 was disclosed as a high-severity insufficient input validation flaw that can cause memory overread in NetScaler ADC and NetScaler Gateway when configured as a SAML Identity Provider. The issue is described as remotely exploitable and vendor fixes were recommended.
Citrix publishes NetScaler advisory covering six CVEs
On 2026-06-30, Citrix published a security advisory for NetScaler ADC, NetScaler Gateway, and certain NetScaler FIPS and NDcPP editions. The advisory covered affected 14.1 and 13.1 release lines and referenced CVE-2026-8451, CVE-2026-8452, CVE-2026-8655, CVE-2026-10816, CVE-2026-10817, and CVE-2026-13474, with updates identified as the remediation.
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Sources
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Citrix Patches Six NetScaler Flaws Allowing File Read and Denial-of-Service
thehackernews.com
Open sourceCitrix patches a new NetScaler flaw with echoes of CitrixBleed | CyberScoop
cyberscoop.com
Open sourceCitrix security advisory (AV26-645) - Canadian Centre for Cyber Security
cyber.gc.ca
Open sourceCVE-2026-8452 - Memory overflow vulnerability leading to unpredictable or erroneous behavior and Denial of Service
cvefeed.io
Open sourceCVE-2026-13474 - Denial of service via malformed HTTP/2 requests
cvefeed.io
Open sourceCVE-2026-8451 - Insufficient input validation leading to memory overread
cvefeed.io
Open sourceMultiple High-Severity Vulnerabilities in Citrix NetScaler ADC and NetScaler Gateway (CVE-2026-8451)
labs.beazley.security
Open sourceCVE-2026-8655 - Multiple Memory overflow vulnerabilities leading to unpredictable or erroneous behavior and Denial of Service
cvefeed.io
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Critical Vulnerabilities Disclosed in Citrix NetScaler ADC and Gateway
Citrix disclosed critical vulnerabilities affecting **NetScaler ADC** and **NetScaler Gateway**, prompting alerts from both the Canadian Centre for Cyber Security and CERT-EU. The issues are tracked as `CVE-2026-3055` and `CVE-2026-4368`, and impact multiple supported release branches, including **14.1**, **13.1**, and **13.1 FIPS/NDcPP** versions running below the vendor’s fixed builds. Affected deployments include standard **NetScaler ADC**, **NetScaler Gateway**, and hardened **FIPS/NDcPP** editions. Government cyber authorities urged organizations to review Citrix’s security bulletin and apply the recommended updates and mitigations without delay. The coordinated advisories indicate broad concern across enterprise and public-sector environments that rely on Citrix application delivery and remote access infrastructure, with administrators advised to identify exposed appliances and move vulnerable systems to patched versions listed by Citrix.
Jul 1, 2026
Critical Citrix NetScaler Flaws Expose ADC and Gateway Appliances
Citrix NetScaler ADC and NetScaler Gateway appliances are affected by multiple critical vulnerabilities that can expose organizations to compromise, including `CVE-2025-5349`, `CVE-2025-5777`, and `CVE-2026-3055`. The flaws impact supported NetScaler releases, while end-of-life versions `12.1` and `13.0` remain vulnerable without fixes. `CVE-2025-5349` enables access-control bypass on the management interface, `CVE-2025-5777` is an out-of-bounds read that can leak sensitive memory contents, and `CVE-2026-3055` is an input-validation flaw that can lead to memory overwrite when NetScaler is configured as a SAML Identity Provider.
Jun 29, 2026
Citrix NetScaler Bulletin Addresses CVE-2026-3055 and CVE-2026-4368
Citrix published a security bulletin for **NetScaler ADC** and **NetScaler Gateway** covering two vulnerabilities tracked as `CVE-2026-3055` and `CVE-2026-4368`. The advisory identifies the affected product line and directs customers to vendor guidance for remediation, signaling that organizations using these edge-access and application delivery platforms should review exposure and apply Citrix-recommended updates or mitigations. Because **NetScaler ADC** and **NetScaler Gateway** are commonly deployed at the network perimeter for remote access, traffic management, and application delivery, the bulletin is relevant to internet-facing infrastructure and remote connectivity services. Security teams should inventory affected appliances, validate version status against the Citrix advisory, and prioritize patching or compensating controls to reduce the risk associated with the two listed CVEs.
Jun 29, 2026