CVE-2017-5542
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 · uneditedCross-site scripting (XSS) vulnerability in template/usererror.missing_extension.php in Symphony CMS before 2.6.10 allows remote attackers to inject arbitrary web script or HTML via the existing-folder parameter.
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 confidenceCross-site scripting (XSS) vulnerability in Symphony CMS template file template/usererror.missing_extension.php allows remote attackers to inject arbitrary web script or HTML via the existing-folder parameter, which is not properly sanitized before output.
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<= 2.6.9CVSS 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:3.0/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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Confirm Symphony CMS installationLook for index.php in the web root, or check for /symphony directory. The presence of a /symphony folder or index.php with Symphony content indicates installation.Affected if Symphony CMS is installed on the server
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Identify installed Symphony versionCheck the Symphony version file (often in /symphony/lib/toolkit/class.system.php or composer.json at the web root), or access the admin panel and look for the version number in the system information or footer.Affected if Version is 2.6.9 or lower
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Locate the vulnerable template fileNavigate to /template/usererror/missing_extension.php within the Symphony installation directory. This path is relative to the Symphony web root.Affected if The file template/usererror/missing_extension.php exists in the installation
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Inspect the existing-folder parameter handlingOpen the file and search for the 'existing-folder' parameter. Check if it is output directly (for example, via echo $_GET['existing-folder']) without sanitization functions like htmlspecialchars() or a similar encoding method.Affected if The existing-folder parameter is output without proper sanitization or encoding
A user is affected if they run Symphony CMS version 2.6.9 or earlier and the template/usererror/missing_extension.php file handles the existing-folder parameter without sanitizing output.
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 dataUpdate to Symphony CMS version 2.6.10 or later, or apply input sanitization/output encoding to the existing-folder parameter in the affected template file.
- Consultation1.0 h
- Implementation1.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,376.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2017-5542 — 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-2017-5542 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
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