CVE-2026-30662: ConcreteCMS v9.4.7 contains a Denial of Service (DoS) vulnerability in the File Manager component

Routine

MEDIUM 6.5DOWNGRADE

CVE-2026-30662 is a medium-severity flaw (CVSS 6.5) affecting concrete cms. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

ConcreteCMS v9.4.7 contains a Denial of Service (DoS) vulnerability in the File Manager component. The 'download' method in 'concrete/controllers/backend/file.php' improperly manages memory when creating zip archives. It uses 'ZipArchive::addFromString' combined with 'file_get_contents', which loads the entire content of every selected file into PHP memory. An authenticated attacker can exploit this by requesting a bulk download of large files, t

Why this priority

Public exploit reference

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

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.3% (top 78%)
CISA exploited list	No
Weakness	CWE-400
Published	2026-03-24
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: concretecms

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

Am I affected?

Timeline

2026-03-24 15:16 UTCPublished CVE record published
2026-06-17 10:32 UTCUpdated Record last modified

concretecms concrete cms DOWNGRADE

Affected: 9.4.7

Fixed in: no fixed release known

Safe to downgrade to: a release before 9.4.7

1. Check installed version

apt-cache policy concrete-cms || rpm -q concrete-cms || concrete-cms --version

2. No fixed release: DOWNGRADE to a release before 9.4.7 (Debian / Ubuntu)

apt-cache madison concrete-cms sudo apt install concrete-cms=<VERSION_BEFORE_9.4.7> sudo apt-mark hold concrete-cms

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

dnf --showduplicates list concrete-cms sudo dnf downgrade concrete-cms-<VERSION_BEFORE_9.4.7> sudo dnf versionlock add concrete-cms

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-2026-30662?

concrete cms: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-30662 being exploited?

CVE-2026-30662 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-2026-30662 affect?

CVE-2026-30662 affects concrete cms. Severity is medium (CVSS 6.5). ConcreteCMS v9.4.7 contains a Denial of Service (DoS) vulnerability in the File Manager component. The 'download' method in 'concrete/controllers/backend/file.php' improperly manages memory when creating zip archives. It uses 'ZipArchive::a

How urgent is CVE-2026-30662?

Priority 33/100. Public exploit reference

Software pages

PHP vulnerabilities

Related CVEs

CVE-2026-18111 MEDIUM 6.1 UPGRADE Concrete CMS 9 before 9.5.3 was vulnerable to stored cross-site scripting (XSS) in the Feature, Feature Link,
CVE-2026-18117 MEDIUM 5.4 UPGRADE Concrete CMS 9.0.0 through 9.5.3 is vulnerable to stored XSS via the custom page alias name (customAliasName)
CVE-2026-68526 MEDIUM 4.3 UPGRADE Concrete CMS before 9.5.3 did not validate an anti-CSRF token in the Calendar event duplicate dialog controlle
CVE-2026-81912 MEDIUM 5.7 UPGRADE Concrete CMS before 9.5.3 is vulnerable to Cross-Site Request Forgery in the Move Multiple Groups feature
CVE-2026-81913 MEDIUM 6.1 UPGRADE Concrete CMS versions 9.5.0 through 9.5.2 are vulnerable to Open Redirect via the rcURL parameter

References

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