How severe is CVE-2021-33511?

CVE-2021-33511 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2021-33511 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (64th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-33511?

CVE-2021-33511 affects Plone. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-33511?

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

When was CVE-2021-33511 published?

CVE-2021-33511 was published on 2021-05-21 and last updated on 2026-06-17.

CVE-2021-33511

CVE-2021-33511 is a high-severity vulnerability in Plone with a CVSS 3.x base score of 7.5. 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-918.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 1% (64th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-918
Affected product: Plone
Published: 2021-05-21
Last modified: 2026-06-17

Description

Plone though 5.2.4 allows SSRF via the lxml parser. This affects Diazo themes, Dexterity TTW schemas, and modeleditors in plone.app.theming, plone.app.dexterity, and plone.supermodel.

Frequently asked questions

What is CVE-2021-33511?: Plone though 5.2.4 allows SSRF via the lxml parser. This affects Diazo themes, Dexterity TTW schemas, and modeleditors in plone.app.theming, plone.app.dexterity, and plone.supermodel.
How severe is CVE-2021-33511?: CVE-2021-33511 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2021-33511 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (64th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-33511?: CVE-2021-33511 affects Plone. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-33511?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-33511 published?: CVE-2021-33511 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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