CVE-2021-33926: An issue in Plone CMS v

This month

HIGH 8.8DOWNGRADE

CVE-2021-33926 is a high-severity flaw (CVSS 8.8) affecting plone. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An issue in Plone CMS v. 5.2.4, 5.2.3, 5.2.2, 5.2.1, 5.2.0, 5.1rc2, 5.1rc1, 5.1b4, 5.1b3, 5.1b2, 5.1a2, 5.1a1, 5.1.7, 5.1.6, 5.1.5, 5.1.4, 5.1.2, 5.1.1 5.1, 5.0rc3, 5.0rc2, 5.0rc1, 5.0.9, 5.0.8, 5.0.7, 5.0.6, 5.0.5, 5.0.4, 5.0.3, 5.0.2, 5.0.10, 5.0.1, 5.0, 4.3.9, 4.3.8, 4.3.7, 4.3.6, 4.3.5, 4.3.4, 4.3.3, 4.3.20, 4 allows attacker to access sensitive information via the RSS feed protlet.

Why this priority

High severity
Public exploit reference

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

Risk facts

CVSS score	8.8 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	1.0% (top 37%)
CISA exploited list	No
Weakness	CWE-918
Published	2023-02-17
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: plone

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

Am I affected?

Timeline

2023-02-17 18:15 UTCPublished CVE record published
2026-06-17 03:55 UTCUpdated Record last modified

plone plone DOWNGRADE

Affected: 4.3 · 4.3.1 · 4.3.2 · 4.3.3 · 4.3.4 · 4.3.5 · 4.3.6 · 4.3.7

Fixed in: no fixed release known

Safe to downgrade to: a release before 4.3

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 4.3 (Debian / Ubuntu)

apt-cache madison plone sudo apt install plone=<VERSION_BEFORE_4.3> sudo apt-mark hold plone

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

dnf --showduplicates list plone sudo dnf downgrade plone-<VERSION_BEFORE_4.3> sudo dnf versionlock add plone

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-2021-33926?

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

Is CVE-2021-33926 being exploited?

CVE-2021-33926 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-2021-33926 affect?

CVE-2021-33926 affects plone. Severity is high (CVSS 8.8). An issue in Plone CMS v. 5.2.4, 5.2.3, 5.2.2, 5.2.1, 5.2.0, 5.1rc2, 5.1rc1, 5.1b4, 5.1b3, 5.1b2, 5.1a2, 5.1a1, 5.1.7, 5.1.6, 5.1.5, 5.1.4, 5.1.2, 5.1.1 5.1, 5.0rc3, 5.0rc2, 5.0rc1, 5.0.9, 5.0.8, 5.0.7, 5.0.6, 5.0.5, 5.0.4, 5.0.3, 5.0.2, 5.0

How urgent is CVE-2021-33926?

Priority 52/100. High severity; Public exploit reference

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References

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