CVE-2008-5840: PHP iCalendar 2.24 and earlier allows remote attackers to bypass authentication by setting the phpicalendar an

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HIGH 7.5UPGRADEDOWNGRADE

CVE-2008-5840 is a high-severity flaw (CVSS 7.5) affecting phpicalendar, phpicalendar2.0. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

PHP iCalendar 2.24 and earlier allows remote attackers to bypass authentication by setting the phpicalendar and phpicalendar_login cookies to 1.

Why this priority

High severity
Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
EPSS exploit chance	3.0% (top 13%)
CISA exploited list	No
Weakness	CWE-264
Published	2009-01-05
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: phpicalendar

Last updated 2026-06-16 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2009-01-05 16:30 UTCPublished CVE record published
2026-06-16 23:01 UTCUpdated Record last modified

phpicalendar phpicalendar UPGRADE

Affected: <= 2.24 · 0.7 · 0.8 · 0.9 · 0.9.5 · 1.0 · 1.1 · 2.0 beta

Fixed in: newer than 2.24

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to newer than 2.24 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade phpicalendar

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade phpicalendar

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

phpicalendar phpicalendar2.0 DOWNGRADE

Affected: alpha_test

Fixed in: no fixed release known

Safe to downgrade to: a release before alpha_test

1. Check installed version

apt-cache policy phpicalendar2.0 || rpm -q phpicalendar2.0 || phpicalendar2.0 --version

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

apt-cache madison phpicalendar2.0 sudo apt install phpicalendar2.0=<VERSION_BEFORE_alpha_test> sudo apt-mark hold phpicalendar2.0

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

dnf --showduplicates list phpicalendar2.0 sudo dnf downgrade phpicalendar2.0-<VERSION_BEFORE_alpha_test> sudo dnf versionlock add phpicalendar2.0

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.

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Exploit-DB: PHP iCalendar 2.24 - Insecure Cookie Handling

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-2008-5840?

phpicalendar: upgrade to newer than 2.24; phpicalendar2.0: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2008-5840 being exploited?

CVE-2008-5840 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-2008-5840 affect?

CVE-2008-5840 affects phpicalendar, phpicalendar2.0. Severity is high (CVSS 7.5). PHP iCalendar 2.24 and earlier allows remote attackers to bypass authentication by setting the phpicalendar and phpicalendar_login cookies to 1.

How urgent is CVE-2008-5840?

Priority 53/100. High severity; Public exploit reference

Software pages

PHP vulnerabilities

Related CVEs

CVE-2008-5968 HIGH 7.5 UPGRADE Directory traversal vulnerability in print.php in PHP iCalendar 2.24 and earlier allows remote attackers to in
CVE-2008-5967 HIGH 7.5 UPGRADE admin/index.php in PHP iCalendar 2.3.4, 2.24, and earlier does not require administrative authentication for a

References

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