CVE-2021-33510Network attack vector

Authenticated file disclosure via permissive iCalendar URL

Published May 21, 2021 · Updated Aug 3, 2024

SSRF in Plone 5.2.4 and earlier allows remote authenticated users with Manager access to read one line of a local file via an event iCalendar URL. The event import check rejects only file:// URLs, so file: relative-path forms reach the URL loader and expose local file content. Manager privileges are required, and the disclosed content is limited to one line from the selected file.

CVSS severity4.3
Medium
EPSS probability0.96%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

SSRF in Plone 5.2.4 and earlier allows remote authenticated users with Manager access to read one line of a local file via an event iCalendar URL. The event import check rejects only file:// URLs, so file: relative-path forms reach the URL loader and expose local file content. Manager privileges are required, and the disclosed content is limited to one line from the selected file.

The record

CVE
CVE-2021-33510
Published
May 21, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-918, T1005
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. May 21, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

4.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
5.3GitHub Advisory DatabaseCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
4.0NIST NVDAV:N/AC:L/Au:S/C:P/I:N/A:N
4.3GitHub Advisory DatabaseCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-918Server-Side Request Forgery (SSRF)
T1005Data from Local System

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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