CVE-2026-3055: Citrix NetScaler Out-of-Bounds Read Vulnerability
Tech GuruQuick Answer
CISA added CVE-2026-3055 to its Known Exploited Vulnerabilities catalog on 2026-03-30, confirming that exploitation has occurred. If you operate Citrix NetScaler, identify the exact version and relevant configuration now, preserve security evidence, and follow the live vendor remediation. A KEV match does not prove your system was compromised, and installing an update does not rule out earlier exploitation.
Operator action
Confirm the exact product, release, exposure, and prerequisites against the live vendor advisory, then apply the vendor-listed update or mitigation. CISA added CVE-2026-3055 to KEV on 2026-03-30.
Last verified: 2026-09-17 UTC. CISA KEV snapshot version
2026.09.16. Recheck the live advisory before changing production.
Context
Status At A Glance
| Product scope | Citrix — NetScaler |
|---|---|
| CVE | CVE-2026-3055 |
| TechGeeks response tier | P0 — confirm an exact match and act now |
| CISA KEV added | 2026-03-30 |
| Vendor severity | Consult the live vendor advisory; no vendor severity is inferred from KEV status. |
| CVSS | Consult the live vendor advisory; no CVSS value is inferred from KEV status. |
| Ransomware field | Unknown — this is not the same as No; CISA has not marked the field Known. |
| Forensic-triage field | No in the current CISA field; organizations should still investigate when exposure or evidence warrants it. |
| CWE | CWE-125 |
| Federal remediation date | 2026-04-02 — applies to covered federal agencies; other organizations should set a risk-based deadline. |
What Happened
Citrix NetScaler Out-of-Bounds Read Vulnerability. Citrix NetScaler ADC (formerly Citrix ADC), NetScaler Gateway (formerly Citrix Gateway) and NetScaler ADC FIPS and NDcPP contain an out-of-bounds reads vulnerability when configured as a SAML IDP leading to memory overread. CISA's KEV listing confirms exploitation evidence, but it does not state how widespread the activity is or prove that any particular installation was compromised.
Affected Scope
Citrix NetScaler ADC (formerly Citrix ADC), NetScaler Gateway (formerly Citrix Gateway) and NetScaler ADC FIPS and NDcPP contain an out-of-bounds reads vulnerability when configured as a SAML IDP leading to memory overread.
Match the exact edition, hardware or virtual platform, release, patch level, enabled feature, and management exposure. A product-family name alone is not enough to establish applicability.
Steps
What To Do Now
- Confirm. Inventory every NetScaler asset and record its exact version, patch level, role, relevant configuration, and exposure.
- Preserve. Save UTC timestamps, off-device authentication, firewall, proxy, DNS, endpoint, application, and SIEM evidence before logs rotate or a disruptive change removes context.
- Contain. Restrict unnecessary internet and management-plane access using supported controls. Follow the live advisory: Open the live Citrix advisory.
- Remediate. Confirm the exact product, release, exposure, and prerequisites against the live vendor advisory, then apply the vendor-listed update or mitigation. CISA added CVE-2026-3055 to KEV on 2026-03-30.
- Validate. Verify the resulting version or patch level, service health, logging, expected access, an expected denial, and representative dependent workflows.
- Escalate. If exposure overlapped the vulnerable period or evidence is suspicious, treat the system as a potential incident and follow vendor and incident-response recovery guidance.
Fixed Releases And Mitigation
Verified fixed release, patch level, or update guidance captured at the last check:
A fixed build or KB was not safely preserved in the research record. Check the live vendor advisory before production changes; do not infer a fixed version from this summary.
Mitigation boundary: Consult the live vendor advisory for the exact affected and fixed release matrix; no release number is asserted here.
A workaround, access restriction, or provider-side control reduces a described path; it does not necessarily remove vulnerable code or erase compromise.
Investigation And Recovery
CISA's KEV record does not mark this entry for forensic triage. That field is not proof of a clean system; consult the vendor advisory for indicators and recovery guidance.
When an attacker may have gained administrative, root, SYSTEM, identity, management-plane, or code-execution access, patching alone is not an eradication claim. Preserve evidence, scope affected accounts and downstream systems, rotate exposed credentials or certificates when justified, and rebuild from a trusted source when vendor or incident-response guidance requires it.
Notes
Exploitation Evidence
Vendor statement: The exact vendor exploitation statement was not safely preserved in the local KEV snapshot; consult the live vendor advisory. Independently, CISA added this vulnerability to KEV on 2026-03-30.
CISA statement: CVE-2026-3055 was added to KEV on 2026-03-30. The ransomware field is Unknown, and the forensic-triage field is No. These are separate signals.
Validation And Boundaries
This notice does not prove that every product carrying the family name is affected, that exploitation is widespread, that a clean indicator search rules out compromise, or that a successful update restored trust. TechGeeks has not reproduced the exploit and does not replace the vendor advisory, asset inventory, vulnerability scanner, or incident-response process.
Related TechGeeks Resources
- Security Hot Page
- All Security Notices
- What to Do When a Device Hits CISA KEV
- Router CVE Exposure, Version, and Mitigation Checklist
- IoT Firmware Update and End-of-Support Checklist
- Live Protect and Runtime Vulnerability Shielding
References
Wrap-Up
Record whether CVE-2026-3055 applies to your environment. If it does, assign an owner, preserve the change and investigation evidence, complete the vendor action, and document the validated result.
Correction policy: If a primary source changes affected versions, remediation, exploitation status, or recovery guidance, TechGeeks will update this page and its verification date.
