What is the CVSS score of CVE-2021-28931?

CVE-2021-28931 has a CVSS 3.1 base score of 8.8 (High). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. EPSS exploitation probability: 1.2%.

Is there a patch available for CVE-2021-28931?

Yes, a patch is available for CVE-2021-28931. Update the affected software to the latest version immediately.

Fork Cms CVE-2021-28931

HIGH

Unrestricted Upload of File with Dangerous Type (CWE-434)

2021-07-07 cve@mitre.org

File Upload Fork Cms

8.8

CVSS 3.1 · NVD

View

Vulnerability Assessment

Weakness	CWE CWE-434 OWASP Top 10:2025 A06:2025 - Insecure Design ASVS 5.0 V5 - File Handling File type validation, storage isolation MITRE ATT&CK 2 techniques across 2 tactics: Command and Control, Persistence The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. Sign in to read
Impact	CVSS score of 8.8 (HIGH). Attack characteristics: network attack vector, low complexity, low privileges required, no user interaction not required.
Exploit ScenarioDerived	A remote attacker could upload malicious files that can be executed on the server by sending crafted requests to the affected application.

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).

Patch available 1.2% exploitation probability (EPSS)

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AnalysisAI

Arbitrary file upload vulnerability in Fork CMS 5.9.2 allows attackers to create or replace arbitrary files in the /themes directory via a crafted zip file uploaded to the Themes panel. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.

RemediationAI

No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Validate file types server-side, store uploads outside webroot, use random filenames, scan for malware.

Affected Packages

composer forkcms/forkcms fix: 5.9.3

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in composer

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

This vulnerability is classified as Unrestricted File Upload (CWE-434), which allows attackers to upload malicious files that can be executed on the server. Arbitrary file upload vulnerability in Fork CMS 5.9.2 allows attackers to create or replace arbitrary files in the /themes directory via a crafted zip file uploaded to the Themes panel. Affected products include: Fork-Cms Fork Cms.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 8.8 HIGH

AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

DescriptionNVD

Arbitrary file upload vulnerability in Fork CMS 5.9.2 allows attackers to create or replace arbitrary files in the /themes directory via a crafted zip file uploaded to the Themes panel.

Threat Intelligence Overview

EPSS Score

1.2%

Top 35% exploitable

Data Quality

3 sources

Confidence: Low

NVD

CVE.org

EPSS

GitHub

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity HIGH

CISA KEV No

Public POC No

EPSS 1.2%

Patch available Yes

Active threat No

Deciding rule

HIGH severity (CVSS 7.0-8.9)

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Scheduled

Exploitation· derived

None

System Exposure· derived

Open

Automatable· derived

Human Impact· derived

Medium

Priority Score

Low Medium High Critical

KEV: 0

EPSS: +1

CVSS: +44

PoC: 0

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Malicious File Upload HIGH

Malicious file upload attacks exploit insufficient validation when web applications accept user-provided files.

Affected Products (CPE)NVD

cpe:2.3:a:fork-cms:fork_cms:5.9.2:*:*:*:*:*:*:*

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PHP object injection in the Ajax endpoint of the backend in ForkCMS below version 5.8.3 allows an authenticated remote u

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SQL injection through marking blog comments on bulk as spam in GitHub repository forkcms/forkcms prior to 5.11.1. Rated

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7.5 Feb 06

Multiple SQL injection vulnerabilities in Translations in Fork CMS before 3.8.6 allow remote authenticated users to exec

CVE-2022-0153 HIGH This Week POC

7.5 Mar 24

SQL Injection in GitHub repository forkcms/forkcms prior to 5.11.1. Rated high severity (CVSS 7.5), this vulnerability i

CVE-2012-1188 MEDIUM This Month POC

4.3 Sep 26

Multiple cross-site scripting (XSS) vulnerabilities in Fork CMS before 3.2.7 allow remote attackers to inject arbitrary

CVE-2012-1208 MEDIUM This Month POC

4.3 Feb 24

Multiple cross-site scripting (XSS) vulnerabilities in backend/core/engine/base.php in Fork CMS 3.2.4 and possibly other

CVE-2019-15521 CRITICAL Act Now

9.8 Aug 26

Spoon Library through 2014-02-06, as used in Fork CMS before 1.4.1 and other products, allows PHP object injection via a

CVE-2022-0145 MEDIUM This Month POC

5.4 Mar 24

Cross-site Scripting (XSS) - Stored in GitHub repository forkcms/forkcms prior to 5.11.1. Rated medium severity (CVSS 5.

CVE-2018-5215 MEDIUM This Month POC

5.4 Jan 04

Fork CMS 5.0.7 has XSS in /private/en/pages/edit via the title parameter. Rated medium severity (CVSS 5.4), this vulnera

CVE-2012-1207 MEDIUM This Month POC

5.0 Feb 24

Directory traversal vulnerability in frontend/core/engine/javascript.php in Fork CMS 3.2.4 and possibly other versions b

CVE-2022-35590 MEDIUM This Month POC

4.8 Aug 12

A cross-site scripting (XSS) issue in the ForkCMS version 5.9.3 allows remote attackers to inject JavaScript via the "en

CVE-2022-35589 MEDIUM This Month POC

4.8 Aug 12

A cross-site scripting (XSS) issue in the Fork version 5.9.3 allows remote attackers to inject JavaScript via the "publi

Same weakness CWE-434 – Unrestricted Upload of File with Dangerous Type

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References

Advisories & patches

REF https://github.com/bousalman/ForkCMS-arbitrary-upload/blob/main/README.md REF https://github.com/forkcms/forkcms/releases/tag/5.9.2

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