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CVE-2017-5542 Getsymphony CVE debrief

CVE-2017-5542 is a cross-site scripting (XSS) vulnerability in Symphony CMS before 2.6.10. The issue affects template/usererror.missing_extension.php and can let a remote attacker inject arbitrary web script or HTML through the existing-folder parameter. NVD classifies the weakness as CWE-79 and assigns CVSS 3.0 6.1 (AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N). The vulnerability was published on 2017-01-20 and later modified in NVD on 2026-05-13. The vendor release notes for 2.6.10 and the linked issue tracker entry are the key references for remediation.

Vendor
Getsymphony
Product
Symphony
CVSS
MEDIUM 6.1
CISA KEV
Not listed in stored evidence
Original CVE published
2017-01-20
Original CVE updated
2026-05-13
Advisory published
2017-01-20
Advisory updated
2026-05-13

Who should care

Operators and maintainers of Symphony CMS instances at version 2.6.9 or earlier, especially internet-facing deployments and teams responsible for content-editing workflows or admin interfaces where user interaction could trigger rendered HTML or script.

Technical summary

The NVD record describes a reflected or rendered XSS condition in Symphony CMS's missing-extension error template. User-controlled input from the existing-folder parameter can reach output in template/usererror.missing_extension.php without adequate escaping, enabling script or HTML injection. NVD maps the issue to CWE-79 and lists the affected CPE range as Symphony versions up to and including 2.6.9, with the fix available in 2.6.10.

Defensive priority

Medium. The issue requires user interaction, but it is network-reachable and can affect confidentiality and integrity in the browser context. Prioritize remediation for public-facing or heavily used CMS deployments.

Recommended defensive actions

  • Upgrade Symphony CMS to version 2.6.10 or later.
  • Inventory all Symphony CMS deployments and confirm no instances remain on 2.6.9 or earlier.
  • Review any customizations around template/usererror.missing_extension.php and verify they preserve output escaping.
  • Treat the existing-folder parameter as attacker-controlled input and ensure it is safely encoded before rendering.
  • If immediate upgrade is not possible, reduce exposure to untrusted users and monitor for anomalous HTML or script injection attempts in affected error paths.

Evidence notes

This debrief is based on the official NVD record and the linked vendor references. The NVD metadata explicitly lists CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N, CWE-79, and vulnerable versions ending at 2.6.9. The provided references include the Symphony CMS issue tracker entry and the 2.6.10 release notes, which indicate the remediation path. No KEV listing was provided for this CVE.

Sources and references

Verified primary and authoritative sources

  • CVE-2017-5542 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2017-5542

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2017-5542 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2017-5542

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.