CVE-2020-20977: A stored cross site scripting (XSS) vulnerability in index.php/legend/6.html of UK CMS v1.1.10 allows attacker

Routine

MEDIUM 5.4DOWNGRADE

CVE-2020-20977 is a medium-severity flaw (CVSS 5.4) affecting ukcms. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A stored cross site scripting (XSS) vulnerability in index.php/legend/6.html of UK CMS v1.1.10 allows attackers to execute arbitrary web scripts or HTML via a crafted payload in the Comments section.

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	0.5% (top 57%)
CISA exploited list	No
Weakness	CWE-79
Published	2021-08-12
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: ukcms

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

Am I affected?

Timeline

2021-08-12 15:15 UTCPublished CVE record published
2026-06-17 03:03 UTCUpdated Record last modified

ukcms ukcms DOWNGRADE

Affected: 1.1.10

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.1.10

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 1.1.10 (Debian / Ubuntu)

apt-cache madison ukcms sudo apt install ukcms=<VERSION_BEFORE_1.1.10> sudo apt-mark hold ukcms

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

dnf --showduplicates list ukcms sudo dnf downgrade ukcms-<VERSION_BEFORE_1.1.10> sudo dnf versionlock add ukcms

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-2020-20977?

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

Is CVE-2020-20977 being exploited?

CVE-2020-20977 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-2020-20977 affect?

CVE-2020-20977 affects ukcms. Severity is medium (CVSS 5.4). A stored cross site scripting (XSS) vulnerability in index.php/legend/6.html of UK CMS v1.1.10 allows attackers to execute arbitrary web scripts or HTML via a crafted payload in the Comments section.

How urgent is CVE-2020-20977?

Priority 35/100. Public exploit reference

Software pages

PHP vulnerabilities

Related CVEs

CVE-2020-18449 MEDIUM 5.4 DOWNGRADE Cross Site Scripting (XSS) vulnerability exists in UKCMS v1.1.10 via data in the index function in Single.php

References

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