CVE-2026-28281: InstantCMS is a free and open source content management system

Q: How do I fix CVE-2026-28281?

instantcms: upgrade to 2.18.1. Exact commands for each OS are on this page.

Q: Is CVE-2026-28281 being exploited?

CVE-2026-28281 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-2026-28281 affect?

CVE-2026-28281 affects instantcms. Severity is high (CVSS 7.1). InstantCMS is a free and open source content management system. Prior to 2.18.1, InstantCMS does not validate CSRF tokens, which allows attackers grant moderator privileges to users, execute scheduled tasks, move posts to trash, and accept

Q: How urgent is CVE-2026-28281?

Priority 31/100. High severity; Public exploit reference

Routine

HIGH 7.1UPGRADE

CVE-2026-28281 is a high-severity flaw (CVSS 7.1) affecting instantcms. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

InstantCMS is a free and open source content management system. Prior to 2.18.1, InstantCMS does not validate CSRF tokens, which allows attackers grant moderator privileges to users, execute scheduled tasks, move posts to trash, and accept friend requests on behalf of the user. This vulnerability is fixed in 2.18.1.

Why this priority

High severity
Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	7.1 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.1% (top 97%)
CISA exploited list	No
Weakness	CWE-352
Published	2026-03-10
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: instantcms

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

Am I affected?

Timeline

2026-03-10 17:38 UTCPublished CVE record published
2026-06-17 10:28 UTCUpdated Record last modified

instantcms instantcms UPGRADE

Affected: < 2.18.1

Fixed in: 2.18.1

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 2.18.1 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade instantcms

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-2026-28281?

instantcms: upgrade to 2.18.1. Exact commands for each OS are on this page.

Is CVE-2026-28281 being exploited?

CVE-2026-28281 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-2026-28281 affect?

CVE-2026-28281 affects instantcms. Severity is high (CVSS 7.1). InstantCMS is a free and open source content management system. Prior to 2.18.1, InstantCMS does not validate CSRF tokens, which allows attackers grant moderator privileges to users, execute scheduled tasks, move posts to trash, and accept

How urgent is CVE-2026-28281?

Priority 31/100. High severity; Public exploit reference

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CVE-2013-10051 CRITICAL 9.8 UPGRADE A remote PHP code execution vulnerability exists in InstantCMS version 1.6 and earlier due to unsafe use of ev

References

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