EsxiOperating system · VMware
CVE-2017-4940
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 · uneditedThe ESXi Host Client in VMware ESXi (6.5 before ESXi650-201712103-SG, 5.5 before ESXi600-201711103-SG and 5.5 before ESXi550-201709102-SG) contains a vulnerability that may allow for stored cross-site scripting (XSS). An attacker can exploit this vulnerability by injecting Javascript, which might get executed when other users access the Host Client.
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 confidenceStored XSS vulnerability in the ESXi Host Client allows an attacker to inject malicious JavaScript that persists and executes when other users access the Host Client web interface. The vulnerability affects ESXi 6.5 before ESXi650-201712103-SG, 5.5 before ESXi600-201711103-SG, and 5.5 before ESXi550-201709102-SG.
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
EsxiOperating system
= 5.5= 6.0= 6.5CVSS 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
- Required
- Scope
- Changed
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/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 checksWork through these to decide whether this CVE applies to you.
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Determine installed ESXi versionRun command 'vmware -v' on the ESXi host shell, or view the version in the vSphere Client under Host > Summary > General information, or query via 'esxcli system version get'Affected if The version shows 5.5.x, 6.0.x, or 6.5.x without the corresponding patch applied (see build numbers below)
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Obtain ESXi build numberRun 'esxcli system version get' or check in vSphere Client under Host > Summary > General information > BuildAffected if Build is earlier than ESXi650-201712103-SG (for 6.5), ESXi600-201711103-SG (for 6.0), or ESXi550-201709102-SG (for 5.5)
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Verify Host Client web interface is accessibleAttempt to access https://[esxi-hostname]/ui or https://[esxi-ip]/ui in a browserAffected if The Host Client web interface loads and accepts input, indicating it is enabled and exposed
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Check if Host Client service is runningRun 'esxcli software vib list | grep -i hostclient' on the ESXi shell, or check via vSphere Client under Host > ServicesAffected if The Host Client VIB package is installed and the service is active (vpxa and/or hostd running)
If ESXi version is 5.5, 6.0, or 6.5 with a build number earlier than the fixed patches (ESXi650-201712103-SG, ESXi600-201711103-SG, or ESXi550-201709102-SG) AND the Host Client web interface is accessible, the environment is affected by this stored XSS vulnerability.
Generated from the published advisory. Verify against your own configuration.
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 dataApply the appropriate VMware security patch (ESXi650-201712103-SG, ESXi600-201711103-SG, or ESXi550-201709102-SG) to the affected ESXi hosts, or upgrade to a patched version. Schedule maintenance windows for production environments.
Fix this in Esxi
Scoped from the published advisory
- Consultation3.0 h
- Implementation4.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,648.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2017-4940 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2017-4940 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- 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