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Application Delivery Controller FirmwareOperating system · Citrix

CVE-2017-17549

MEDIUM · 5.9 CVSS v3.0 Published 2017-12-13
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
68/100
Remediation priority · Elevated
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
Citrix NetScaler Application Delivery Controller (ADC) and NetScaler Gateway 10.5 before build 67.13, 11.0 before build 71.22, 11.1 before build 56.19, and 12.0 before build 53.22 allow remote attackers to obtain sensitive information from the backend client TLS handshake by leveraging use of TLS with Client Certificates and a Diffie-Hellman Ephemeral (DHE) key exchange.

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

Citrix NetScaler ADC and Gateway leak sensitive information during TLS handshakes when client certificates are used together with Diffie-Hellman Ephemeral (DHE) key exchange. An unauthenticated remote attacker can exploit this timing or implementation flaw to extract secrets from the TLS handshake, potentially compromising mutual TLS authentication.

MitigationUpgrade Citrix NetScaler to version 10.5 build 67.13+, 11.0 build 71.22+, 11.1 build 56.19+, or 12.0 build 53.22+. Alternatively, if DHE is not required, consider using ECDHE key exchange or disabling DHE ciphersuites until patching is feasible.

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
Application Delivery Controller FirmwareOperating system
Affected:= 10.5= 11.0= 11.1= 12.0
Netscaler Gateway FirmwareOperating system
Affected:= 10.5= 11.0= 11.1= 12.0

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
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

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 the NetScaler product and firmware version
    Log into the NetScaler CLI and run 'show version' or check the GUI under System > Information > Version. Note the exact firmware build number.
    Affected if The firmware version is 10.5, 11.0, 11.1, or 12.0 at any build (these are the affected version branches)
  2. Confirm the specific build number is vulnerable
    Compare your exact build number against the fixed releases: build 67.13 or higher for 10.5, build 71.22 or higher for 11.0, build 56.19 or higher for 11.1, build 53.22 or higher for 12.0.
    Affected if Your build number is lower than the fixed build for your version branch (e.g., 11.0 build 55.0 is below 71.22)
  3. Verify TLS client certificate authentication is enabled
    Check the SSL virtual server or SSL profile configuration by running 'show ssl vserver <name>' or 'show ssl profile <name>' and look for 'client authentication' setting.
    Affected if Client authentication is set to Mandatory or Optional (the flaw requires mutual TLS with client certificates)
  4. Check if DHE ciphersuites are enabled
    Run 'show ssl cipher' or inspect the cipher group bound to your SSL vserver/profile. Look for DHE-based cipher suites (e.g., DHE-RSA-AES256-SHA, DHE-RSA-AES128-SHA).
    Affected if DHE-based cipher suites are in the enabled cipher list (the flaw requires DHE key exchange to be active)

You are affected if you are running a NetScaler ADC or Gateway on version 10.5, 11.0, 11.1, or 12.0 below the fixed builds AND you have both client certificate authentication enabled AND DHE cipher suites in use on your SSL configuration.

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.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade Citrix NetScaler to version 10.5 build 67.13+, 11.0 build 71.22+, 11.1 build 56.19+, or 12.0 build 53.22+. Alternatively, if DHE is not required, consider using ECDHE key exchange or disabling DHE ciphersuites until patching is feasible.

Fix this in Application Delivery Controller Firmware Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
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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-2017-17549 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