CVE-2017-5542: Cross-site scripting (XSS) vulnerability in template/usererror.missing_extension.php in Symphony CMS before 2.

Q: How do I fix CVE-2017-5542?

symphony: upgrade to newer than 2.6.9. Exact commands for each OS are on this page.

Q: Is CVE-2017-5542 being exploited?

CVE-2017-5542 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2017-5542 affect?

CVE-2017-5542 affects symphony. Severity is medium (CVSS 6.1). Cross-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.

Q: How urgent is CVE-2017-5542?

Priority 38/100. No elevated risk signals yet.

Routine

MEDIUM 6.1UPGRADE

CVE-2017-5542 is a medium-severity flaw (CVSS 6.1) affecting symphony. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Cross-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.

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	6.1 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	1.2% (top 33%)
CISA exploited list	No
Weakness	CWE-79
Published	2017-01-20
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: getsymphony

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2017-01-20 08:59 UTCPublished CVE record published
2026-06-17 01:20 UTCUpdated Record last modified

getsymphony symphony UPGRADE

Affected: <= 2.6.9

Fixed in: newer than 2.6.9

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy symphony || rpm -q symphony || symphony --version

2. UPGRADE to newer than 2.6.9 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade symphony

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade symphony

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2017-5542?

symphony: upgrade to newer than 2.6.9. Exact commands for each OS are on this page.

Is CVE-2017-5542 being exploited?

CVE-2017-5542 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2017-5542 affect?

CVE-2017-5542 affects symphony. Severity is medium (CVSS 6.1). Cross-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.

How urgent is CVE-2017-5542?

Priority 38/100. No elevated risk signals yet.

Software pages

PHP vulnerabilities

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References

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