FortiwlcApplication · Fortinet
CVE-2021-26087
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 · uneditedAn improper neutralization of input during web page generation in FortiWLC version 8.6.0, version 8.5.3 and below, version 8.4.8 and below, version 8.3.3 web interface may allow both authenticated remote attackers and non-authenticated attackers in the same network as the appliance to perform a stored cross site scripting attack (XSS) via injecting malicious payloads in different locations.
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 confidenceFortiWLC web interface versions 8.6.0, 8.5.3 and below, 8.4.8 and below, and 8.3.3 contain a stored cross-site scripting (XSS) vulnerability. Both authenticated remote attackers and unauthenticated attackers on the same network can inject malicious JavaScript payloads into multiple web interface fields, which are then stored and executed when other users view the affected pages.
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
FortiwlcApplication
>= 8.4.0, <= 8.4.2>= 8.4.4, < 8.5.4= 8.3.3= 8.6.0CVSS 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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Identify FortiWLC web interface versionLog into the FortiWLC controller or check system information page to determine the installed firmware version. This is typically found in the system dashboard or about section of the web management interface.Affected if The version falls within these ranges: 8.3.3, 8.4.0 through 8.4.2, 8.4.4 through 8.5.3, or exactly 8.6.0
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Confirm web interface is accessibleVerify that the FortiWLC web management interface (HTTPS on ports 443 or 8080 typically) is reachable from the network. Check if the interface is listening on expected ports.Affected if The web interface is exposed to network access, particularly to untrusted users or the same network segment as untrusted attackers
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Review web interface for unexpected scriptsInspect page source or use browser developer tools to examine stored values in web form fields. Look for script tags, javascript: URLs, or event handlers in fields where user input is stored and displayed.Affected if Malicious JavaScript payloads appear stored in web interface fields such as system configuration, user profiles, or network settings pages
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Check browser console for XSS errorsAccess the FortiWLC web interface using a browser and open the developer console. Navigate through different pages while monitoring for JavaScript errors or unexpected script executions.Affected if JavaScript errors or unexpected script execution occurs when viewing certain pages, indicating injected code is present
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Audit recent administrative changesReview system logs and audit trails for any unexpected configuration changes or new entries in web interface fields that were not made by legitimate administrators.Affected if Unknown or unauthorized changes appear in logs, or configuration entries contain suspicious character sequences typical of XSS payloads
A user is affected if their FortiWLC version is 8.3.3, 8.4.0-8.4.2, 8.4.4-8.5.3, or 8.6.0 AND the web interface is network-accessible to potential attackers who could inject stored XSS payloads.
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 data8.5.4
Apply vendor patches for FortiWLC (upgrade to patched version). Implement input validation and output encoding on all web interface input fields as an interim mitigation.
Fix this in Fortiwlc
Scoped from the published advisory
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $6,176.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-26087 — 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-2021-26087 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
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