CVE-2021-24927: The My Calendar WordPress plugin before 3.2.18 does not sanitise and escape the callback parameter of the mc_p

Q: How do I fix CVE-2021-24927?

my calendar: upgrade to 3.2.18. Exact commands for each OS are on this page.

Q: Is CVE-2021-24927 being exploited?

CVE-2021-24927 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-2021-24927 affect?

CVE-2021-24927 affects my calendar. Severity is medium (CVSS 5.4). The My Calendar WordPress plugin before 3.2.18 does not sanitise and escape the callback parameter of the mc_post_lookup AJAX action (available to any authenticated user) before outputting it back in the response, leading to a Reflected Cro

Q: How urgent is CVE-2021-24927?

Priority 36/100. Public exploit reference

Routine

MEDIUM 5.4UPGRADE

CVE-2021-24927 is a medium-severity flaw (CVSS 5.4) affecting my calendar. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The My Calendar WordPress plugin before 3.2.18 does not sanitise and escape the callback parameter of the mc_post_lookup AJAX action (available to any authenticated user) before outputting it back in the response, leading to a Reflected Cross-Site Scripting issue

Why this priority

Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	5.4 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	Required
EPSS exploit chance	0.6% (top 50%)
CISA exploited list	No
Weakness	CWE-79
Published	2021-11-29
Last modified	2026-06-17

Publisher (CNA): WPScan · Vendor: my calendar project

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

Am I affected?

Timeline

2021-11-29 09:15 UTCPublished CVE record published
2026-06-17 03:41 UTCUpdated Record last modified

my calendar project my calendar UPGRADE

Affected: < 3.2.18

Fixed in: 3.2.18

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 3.2.18 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade my-calendar

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-2021-24927?

my calendar: upgrade to 3.2.18. Exact commands for each OS are on this page.

Is CVE-2021-24927 being exploited?

CVE-2021-24927 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-2021-24927 affect?

CVE-2021-24927 affects my calendar. Severity is medium (CVSS 5.4). The My Calendar WordPress plugin before 3.2.18 does not sanitise and escape the callback parameter of the mc_post_lookup AJAX action (available to any authenticated user) before outputting it back in the response, leading to a Reflected Cro

How urgent is CVE-2021-24927?

Priority 36/100. Public exploit reference

Software pages

WordPress vulnerabilities

Related CVEs

CVE-2024-1274 MEDIUM 5.4 UPGRADE The My Calendar WordPress plugin before 3.4.24 does not sanitise and escape some parameters, which could allow
CVE-2023-6360 HIGH 8.6 UPGRADE The 'My Calendar' WordPress Plugin, version < 3.4.22 is affected by an unauthenticated SQL injection vulnerabi
CVE-2023-23813 MEDIUM 5.4 UPGRADE Cross-Site Request Forgery (CSRF) vulnerability in Joseph C Dolson My Calendar plugin <= 3.4.3 versions.
CVE-2022-47427 MEDIUM 5.4 UPGRADE Cross-Site Request Forgery (CSRF) vulnerability in Joseph C Dolson My Calendar plugin <= 3.3.24.1 versions.
CVE-2019-15713 MEDIUM 6.1 UPGRADE The my-calendar plugin before 3.1.10 for WordPress has XSS.

References

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