CVE-2020-18455: Cross Site Scripting (XSS) vulnerability exists in bycms v3.0.4 via the title parameter in the edit function i

Routine

MEDIUM 4.8DOWNGRADE

CVE-2020-18455 is a medium-severity flaw (CVSS 4.8) affecting bycms. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Cross Site Scripting (XSS) vulnerability exists in bycms v3.0.4 via the title parameter in the edit function in Document.php.

Why this priority

Public exploit reference

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

Risk facts

CVSS score	4.8 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	High
User interaction	Required
EPSS exploit chance	0.5% (top 55%)
CISA exploited list	No
Weakness	CWE-79
Published	2021-08-12
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: bycms project

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 18:15 UTCPublished CVE record published
2026-06-17 02:59 UTCUpdated Record last modified

bycms project bycms DOWNGRADE

Affected: 1.3.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.3.0

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 1.3.0 (Debian / Ubuntu)

apt-cache madison bycms sudo apt install bycms=<VERSION_BEFORE_1.3.0> sudo apt-mark hold bycms

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

dnf --showduplicates list bycms sudo dnf downgrade bycms-<VERSION_BEFORE_1.3.0> sudo dnf versionlock add bycms

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-2020-18455?

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

Is CVE-2020-18455 being exploited?

CVE-2020-18455 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-2020-18455 affect?

CVE-2020-18455 affects bycms. Severity is medium (CVSS 4.8). Cross Site Scripting (XSS) vulnerability exists in bycms v3.0.4 via the title parameter in the edit function in Document.php.

How urgent is CVE-2020-18455?

Priority 33/100. Public exploit reference

Software pages

PHP vulnerabilities

Related CVEs

CVE-2020-18457 MEDIUM 6.8 DOWNGRADE Cross Site Request Forgery (CSRF) vulnerability exists in bycms v1.3.0 that can add an admin account via admin
CVE-2020-18454 MEDIUM 6.8 DOWNGRADE Cross Site Request Forgery (CSRF) vulnerability in bycms v1.3 via admin.php/systems/index/module_id/70/group_i

References

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