HOMEVULNERABILITIESCVE-2021-33199
CRITICAL

CVE-2021-33199

CWE-20Published: August 12, 2021· Updated: Jun 17, 2026

9.8
CVSS v3.1

Official Description

In Expression Engine before 6.0.3, addonIcon in Addons/file/mod.file.php relies on the untrusted input value of input->get('file') instead of the fixed file names of icon.png and icon.svg.

NVD Source

Technical Analysis

CVE-2021-33199 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 9.8.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.None
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected Vendors & Products

expressionengine1 product(s)
expressionengine
Source: NVD CPE · 1 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
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Official Patches & Advisories

PATCHhttps://github.com/ExpressionEngine/ExpressionEngine/compare/6.0.1...6.0.3#diff-17bcb23e5666fc2dccb79c7133e9eeb701847f67ae84fbde0a673c3fd3d109e0R508
PATCHhttps://github.com/ExpressionEngine/ExpressionEngine/compare/6.0.1...6.0.3#diff-17bcb23e5666fc2dccb79c7133e9eeb701847f67ae84fbde0a673c3fd3d109e0R508
ADVISORYhttps://github.com/ExpressionEngine/ExpressionEngine/releases/tag/6.0.3
ADVISORYhttps://github.com/ExpressionEngine/ExpressionEngine/releases/tag/6.0.3

All References (4)

→
https://github.com/ExpressionEngine/ExpressionEngine/compare/6.0.1...6.0.3#diff-17bcb23e5666fc2dccb79c7133e9eeb701847f67ae84fbde0a673c3fd3d109e0R508Patch · Third Party Advisory
→
https://github.com/ExpressionEngine/ExpressionEngine/releases/tag/6.0.3Release Notes · Third Party Advisory
→
https://github.com/ExpressionEngine/ExpressionEngine/compare/6.0.1...6.0.3#diff-17bcb23e5666fc2dccb79c7133e9eeb701847f67ae84fbde0a673c3fd3d109e0R508Patch · Third Party Advisory
→
https://github.com/ExpressionEngine/ExpressionEngine/releases/tag/6.0.3Release Notes · Third Party Advisory

Quick Facts

CVE IDCVE-2021-33199
CVSS Score9.8 / 10
SeverityCRITICAL
WeaknessCWE-20
CISA KEVNo
Affected1 vendor(s)
PublishedAug 12, 2021

Related CVEs (CWE-20)

CVE-2008-4329
10.0
CVE-2007-0213
10.0
CVE-2020-6962
10.0
CVE-2008-4910
10.0
CVE-2025-34105
10.0
CVE-2026-33587
10.0

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2021-33199 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWatch. CVE data is provided under the NVD usage policy.
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