How severe is CVE-2021-33509?

CVE-2021-33509 has a CVSS 3.x base score of 9.9, rated critical severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-33509 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (79th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-33509?

CVE-2021-33509 affects Plone. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-33509?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-33509 published?

CVE-2021-33509 was published on 2021-05-21 and last updated on 2026-06-17.

CVE-2021-33509

CVE-2021-33509 is a critical-severity vulnerability in Plone with a CVSS 3.x base score of 9.9. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-732.

Key facts

Severity: Critical (CVSS 3.x base score 9.9)
CVSS v2: 8.5
EPSS exploit prediction: 2% (79th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-732
Affected product: Plone
Published: 2021-05-21
Last modified: 2026-06-17

Description

Plone through 5.2.4 allows remote authenticated managers to perform disk I/O via crafted keyword arguments to the ReStructuredText transform in a Python script.

Frequently asked questions

What is CVE-2021-33509?: Plone through 5.2.4 allows remote authenticated managers to perform disk I/O via crafted keyword arguments to the ReStructuredText transform in a Python script.
How severe is CVE-2021-33509?: CVE-2021-33509 has a CVSS 3.x base score of 9.9, rated critical severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-33509 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (79th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-33509?: CVE-2021-33509 affects Plone. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-33509?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-33509 published?: CVE-2021-33509 was published on 2021-05-21 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:plone:plone:*:*:*:*:*:*:*:*

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