CVE-2021-34667: The Calendar_plugin WordPress plugin is vulnerable to Reflected Cross-Site Scripting due to the use of `$_SERV

Q: How do I fix CVE-2021-34667?

calendar plugin: upgrade to newer than 1.0. Exact commands for each OS are on this page.

Q: Is CVE-2021-34667 being exploited?

CVE-2021-34667 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-2021-34667 affect?

CVE-2021-34667 affects calendar plugin. Severity is medium (CVSS 6.1). The Calendar_plugin WordPress plugin is vulnerable to Reflected Cross-Site Scripting due to the use of `$_SERVER['PHP_SELF']` in the ~/calendar.php file which allows attackers to inject arbitrary web scripts, in versions up to and including

Q: How urgent is CVE-2021-34667?

Priority 41/100. Public exploit reference

This month

MEDIUM 6.1UPGRADE

CVE-2021-34667 is a medium-severity flaw (CVSS 6.1) affecting calendar plugin. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The Calendar_plugin WordPress plugin is vulnerable to Reflected Cross-Site Scripting due to the use of `$_SERVER['PHP_SELF']` in the ~/calendar.php file which allows attackers to inject arbitrary web scripts, in versions up to and including 1.0.

Why this priority

Public exploit reference

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	0.9% (top 41%)
CISA exploited list	No
Weakness	CWE-79
Published	2021-08-16
Last modified	2026-06-17

Publisher (CNA): Wordfence · Vendor: calendar plugin project

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

Am I affected?

Timeline

2021-08-16 19:15 UTCPublished CVE record published
2026-06-17 03:56 UTCUpdated Record last modified

calendar plugin project calendar plugin UPGRADE

Affected: <= 1.0

Fixed in: newer than 1.0

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy calendar-plugin || rpm -q calendar-plugin || calendar-plugin --version

2. UPGRADE to newer than 1.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade calendar-plugin

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade calendar-plugin

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-2021-34667?

calendar plugin: upgrade to newer than 1.0. Exact commands for each OS are on this page.

Is CVE-2021-34667 being exploited?

CVE-2021-34667 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-2021-34667 affect?

CVE-2021-34667 affects calendar plugin. Severity is medium (CVSS 6.1). The Calendar_plugin WordPress plugin is vulnerable to Reflected Cross-Site Scripting due to the use of `$_SERVER['PHP_SELF']` in the ~/calendar.php file which allows attackers to inject arbitrary web scripts, in versions up to and including

How urgent is CVE-2021-34667?

Priority 41/100. Public exploit reference

Software pages

WordPress vulnerabilities · PHP vulnerabilities

References

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