CVE-2021-42078: PHP Event Calendar through 2021-11-04 allows persistent cross-site scripting (XSS), as demonstrated by the /se

This month

MEDIUM 6.1DOWNGRADE

CVE-2021-42078 is a medium-severity flaw (CVSS 6.1) affecting php event calendar. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

PHP Event Calendar through 2021-11-04 allows persistent cross-site scripting (XSS), as demonstrated by the /server/ajax/events_manager.php title parameter. This can be exploited by an adversary in multiple ways, e.g., to perform actions on the page in the context of other users, or to deface the site.

Why this priority

Public exploit reference

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

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	2021-11-08
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: php event calendar project

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

Am I affected?

Timeline

2021-11-08 05:15 UTCPublished CVE record published
2026-06-17 04:09 UTCUpdated Record last modified

php event calendar project php event calendar DOWNGRADE

Affected: 2021-11-04

Fixed in: no fixed release known

Safe to downgrade to: a release before 2021-11-04

1. Check installed version

apt-cache policy php-event-calendar || rpm -q php-event-calendar || php-event-calendar --version

2. No fixed release: DOWNGRADE to a release before 2021-11-04 (Debian / Ubuntu)

apt-cache madison php-event-calendar sudo apt install php-event-calendar=<VERSION_BEFORE_2021-11-04> sudo apt-mark hold php-event-calendar

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

dnf --showduplicates list php-event-calendar sudo dnf downgrade php-event-calendar-<VERSION_BEFORE_2021-11-04> sudo dnf versionlock add php-event-calendar

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-2021-42078?

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

Is CVE-2021-42078 being exploited?

CVE-2021-42078 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-2021-42078 affect?

CVE-2021-42078 affects php event calendar. Severity is medium (CVSS 6.1). PHP Event Calendar through 2021-11-04 allows persistent cross-site scripting (XSS), as demonstrated by the /server/ajax/events_manager.php title parameter. This can be exploited by an adversary in multiple ways, e.g., to perform actions on

How urgent is CVE-2021-42078?

Priority 41/100. Public exploit reference

Software pages

PHP vulnerabilities

Related CVEs

CVE-2021-42077 CRITICAL 9.8 UPGRADE PHP Event Calendar before 2021-09-03 allows SQL injection, as demonstrated by the /server/ajax/user_manager.ph

References

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