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Actively exploited in the wild. This CVE is on the CISA Known Exploited Vulnerabilities list — treat remediation as urgent. Federal remediation due by 7 Feb 2024.
Netscaler Application Delivery ControllerApplication · Citrix

CVE-2023-6549

HIGH · 7.5 CVSS v3.1 Published 2024-01-17
Fix available
A fix is available. Upgrade to 12.1-55.302 / 13.0-92.21 or later.
See remediation →
100/100
Remediation priority · Urgent
In the wild High EPSS Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Improper Restriction of Operations within the Bounds of a Memory Buffer in NetScaler ADC and NetScaler Gateway allows Unauthenticated Denial of Service and Out-Of-Bounds Memory Read

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A buffer boundary validation flaw in NetScaler ADC and NetScaler Gateway allows unauthenticated attackers to trigger a denial of service condition and perform out-of-bounds memory reads. The vulnerability stems from improper restriction of memory buffer operations, enabling attackers to access memory outside allocated boundaries without authentication.

MitigationApply the vendor patch released by Citrix for NetScaler ADC and NetScaler Gateway. Prior to deployment, validate the patch in a non-production environment and ensure backup configurations are available.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Netscaler Application Delivery ControllerApplication
Affected:>= 12.1, < 12.1-55.302>= 13.0, < 13.0-92.21>= 13.1, < 13.1-37.176>= 13.1, < 13.1-51.15>= 14.1, < 14.1-12.35
Netscaler GatewayApplication
Affected:>= 13.0, < 13.0-92.21>= 13.1, < 13.1-51.15>= 14.1, < 14.1-12.35

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify if NetScaler ADC or Gateway is deployed
    Check system inventory or network documentation for Citrix NetScaler Application Delivery Controller or NetScaler Gateway appliances in the environment
    Affected if The product is NetScaler ADC or NetScaler Gateway
  2. Retrieve the installed NetScaler version
    Run the command 'show version' or 'nsversion' on the NetScaler command line interface, or check the version displayed in the NetScaler management GUI under System > Information
    Affected if Unable to retrieve a version number indicates the system may not be NetScaler
  3. Compare the installed version against affected ranges
    Match the retrieved version to these ranges: ADC 12.1 before 55.302, ADC/Gateway 13.0 before 92.21, ADC 13.1 before 37.176 or before 51.15, ADC/Gateway 14.1 before 12.35
    Affected if The installed version falls within any of these ranges: 12.1-12.1-55.301, 13.0-13.0-92.20, 13.1-13.1-37.175 or 13.1-13.1-51.14, 14.1-14.1-12.34
  4. Confirm management interface exposure
    Determine if the NetScaler management interface (NSIP/Management IP) is accessible from untrusted networks or the internet
    Affected if The management interface is externally accessible and the version is affected, increasing exploitation likelihood

If the system runs NetScaler ADC or Gateway and the installed version matches any of the listed affected ranges, the environment is vulnerable to CVE-2023-6549.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 12.1-55.302 / 13.0-92.21 / 13.1-37.176 or later
Fixed in 12.1-55.30213.0-92.2113.1-37.176
Interim mitigation

Apply the vendor patch released by Citrix for NetScaler ADC and NetScaler Gateway. Prior to deployment, validate the patch in a non-production environment and ensure backup configurations are available.

Recommended fix High confidence

NetScaler ADC 12.1 -> 12.1-55.302; ADC 13.0 -> 13.0-92.21; ADC/Gateway 13.1 -> 13.1-51.15; Gateway 14.1 -> 14.1-12.35

  1. 1. Identify the current NetScaler ADC and/or NetScaler Gateway version installed in your environment
  2. 2. For NetScaler ADC 12.1: Upgrade to version 12.1-55.302 or later
  3. 3. For NetScaler ADC 13.0: Upgrade to version 13.0-92.21 or later
  4. 4. For NetScaler ADC 13.1: Upgrade to version 13.1-51.15 or later (note: earlier 13.1 versions may need intermediate upgrade to 13.1-37.176 first)
  5. 5. For NetScaler Gateway 13.0: Upgrade to version 13.0-92.21 or later
  6. 6. For NetScaler Gateway 13.1: Upgrade to version 13.1-51.15 or later
  7. 7. For NetScaler Gateway 14.1: Upgrade to version 14.1-12.35 or later
  8. 8. After upgrade, verify the new version is running and confirm the vulnerability is remediated
Caveat Review Citrix release notes for each target version for any deprecated features, configuration changes, or compatibility considerations before upgrading

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Netscaler Application Delivery Controller Exploited in the wild — priority engagement
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
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An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,088.

Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2023-6549 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data