CVE-2020-21656: XYHCMS v3.6 contains a stored cross-site scripting (XSS) vulnerability in the component xyhai.php?s=/Link/inde

Routine

MEDIUM 5.4DOWNGRADE

CVE-2020-21656 is a medium-severity flaw (CVSS 5.4) affecting xyhcms. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

XYHCMS v3.6 contains a stored cross-site scripting (XSS) vulnerability in the component xyhai.php?s=/Link/index.

Why this priority

Public exploit reference

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

Risk facts

CVSS score	5.4 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	Required
EPSS exploit chance	0.4% (top 61%)
CISA exploited list	No
Weakness	CWE-79
Published	2021-10-06
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: xyhcms

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

Am I affected?

Timeline

2021-10-06 22:15 UTCPublished CVE record published
2026-06-17 03:03 UTCUpdated Record last modified

xyhcms xyhcms DOWNGRADE

Affected: 3.6

Fixed in: no fixed release known

Safe to downgrade to: a release before 3.6

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 3.6 (Debian / Ubuntu)

apt-cache madison xyhcms sudo apt install xyhcms=<VERSION_BEFORE_3.6> sudo apt-mark hold xyhcms

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

dnf --showduplicates list xyhcms sudo dnf downgrade xyhcms-<VERSION_BEFORE_3.6> sudo dnf versionlock add xyhcms

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-2020-21656?

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

Is CVE-2020-21656 being exploited?

CVE-2020-21656 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-2020-21656 affect?

CVE-2020-21656 affects xyhcms. Severity is medium (CVSS 5.4). XYHCMS v3.6 contains a stored cross-site scripting (XSS) vulnerability in the component xyhai.php?s=/Link/index.

How urgent is CVE-2020-21656?

Priority 34/100. Public exploit reference

Software pages

PHP vulnerabilities

Related CVEs

CVE-2020-20586 MEDIUM 4.5 DOWNGRADE A cross site request forgery (CSRF) vulnerability in the /xyhai.php?s=/Auth/editUser URI of XYHCMS V3.6 allows

References

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