CVE-2021-38710: Static (Persistent) XSS Vulnerability exists in version 4.3.0 of Yclas when using the install/view/form.php sc

Routine

MEDIUM 6.1DOWNGRADE

CVE-2021-38710 is a medium-severity flaw (CVSS 6.1) affecting yclas. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Static (Persistent) XSS Vulnerability exists in version 4.3.0 of Yclas when using the install/view/form.php script. An attacker can store XSS in the database through the vulnerable SITE_NAME parameter.

Why this priority

No elevated risk signals yet

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	6.1 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.6% (top 50%)
CISA exploited list	No
Weakness	CWE-79
Published	2021-08-18
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: yclas

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

Am I affected?

Timeline

2021-08-18 15:15 UTCPublished CVE record published
2026-06-17 04:02 UTCUpdated Record last modified

yclas yclas DOWNGRADE

Affected: 4.3.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 4.3.0

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 4.3.0 (Debian / Ubuntu)

apt-cache madison yclas sudo apt install yclas=<VERSION_BEFORE_4.3.0> sudo apt-mark hold yclas

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list yclas sudo dnf downgrade yclas-<VERSION_BEFORE_4.3.0> sudo dnf versionlock add yclas

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

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-2021-38710?

yclas: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-38710 being exploited?

CVE-2021-38710 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-2021-38710 affect?

CVE-2021-38710 affects yclas. Severity is medium (CVSS 6.1). Static (Persistent) XSS Vulnerability exists in version 4.3.0 of Yclas when using the install/view/form.php script. An attacker can store XSS in the database through the vulnerable SITE_NAME parameter.

How urgent is CVE-2021-38710?

Priority 34/100. No elevated risk signals yet.

Software pages

PHP vulnerabilities

References

← Back to latest CVEs