CVE-2021-28931

HIGH

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.

Affects 1 product across 1 vendor.

CVSS 3.18.8
EPSS1.2%
Percentile68th
PatchUnknown
CVSS Vector — Plain English Remotely exploitable over the network, low complexity, low privileges required, no user interaction needed, impact contained to the vulnerable component, full confidentiality impact, full integrity impact, full availability impact.
CWE Weakness Definitions
CWE-434: Unrestricted Upload of File with Dangerous Type

Application allows file uploads without validating type, enabling upload of executable code or web shells.

Related Attack Patterns (CAPEC)
CAPEC-1 Accessing Functionality Not Properly Constrained by ACLs
via CWE-434

Mapping is CWE-to-CAPEC per MITRE CAPEC 3.9.

◆ AI Analysis — automated analysis, not human-reviewed

A critical vulnerability in Fork CMS 5.9.2 allows attackers to upload arbitrary files to the /themes directory, potentially leading to remote code execution.

BSID: BS-2021-GLOBAL-076993-H • Model: /workspace/models/qwen2.5-coder-32b-instruct-bf16 • Confidence: HIGH

Is this CVE in your environment?

BreachSpider monitors your ICS/OT environment for vulnerabilities like this one. No agents or network access required. Free to start.

Check My Environment →
Frequently Asked Questions
What is CVE-2021-28931?
A critical vulnerability in Fork CMS 5.9.2 allows attackers to upload arbitrary files to the /themes directory, potentially leading to remote code execution.
What is the CVSS score for CVE-2021-28931?
CVE-2021-28931 has CVSS 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. EPSS: 1.2%.
Is CVE-2021-28931 actively exploited?
No confirmed active exploitation of CVE-2021-28931 as of 2026-09-25.
How do I remediate CVE-2021-28931?
Priority: IMMEDIATE.
What systems are affected by CVE-2021-28931?
CVE-2021-28931 affects Fork-Cms Fork Cms.
Vulnerability Details
CVE IDCVE-2021-28931
BSIDBS-2021-GLOBAL-076993-H BreachSpider Global ID
CVSS VectorCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Published2021-07-07
Last Modified2026-06-17
ICS Relevance0%
Weakness (CWE)
Unrestricted Upload of File with Dangerous Type
SourceNVD
Official Description

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.

Source: NIST NVD / MITRE CVE Database

Attack Vector Analysis — CITED Relevance

The vulnerability is exploited by uploading a crafted zip file through the Themes panel, which can then be used to create or replace files in the /themes directory.

Exploitation Likelihood: HIGH

Affected Products
VendorProductAffected Versions
Fork-Cms Fork Cms 5.9.2
Remediation

No official vendor advisory link on record. See the CVE record →

Threat Intelligence
● Threat Intelligence Validated: October 2026 | Threat Age: 1926 Days
CISA known-exploitedNot in KEV catalog
Public ExploitNot confirmed
PoC CodeNot confirmed
AI Enrichment Record — provenance & audit hash
Model/workspace/models/qwen2.5-coder-32b-instruct-bf16
ConfidenceHIGH
Enriched At2026-05-24
SHA-512 Audit Hash9c04a820623b687edb1c6f03b7817cd86010412eb6c1dc42a214d37559e9857ac6ce7031bc3f7b82237782fb805ff3302568df637ff5292af97a340da09b1bbc
Related CVEs affecting Fork-Cms
CVE-2019-15521 9.8 Spoon Library through 2014-02-06, as used in Fork CMS before 1.4.1 and other ... CVE-2020-24036 8.8 PHP object injection in the Ajax endpoint of the backend in ForkCMS below ver... CVE-2020-23264 8.8 Cross-site request forgery (CSRF) in Fork-CMS before 5.8.2 allow remote attac... CVE-2020-23960 8.8 Multiple cross-site request forgery (CSRF) vulnerabilities in the Admin Conso... CVE-2022-1064 8.8 SQL injection through marking blog comments on bulk as spam in GitHub reposit...
View all Fork-Cms CVEs →

ICS/OT Vulnerability Intelligence for Your Environment

BreachSpider tracks 384,000+ CVEs and matches them to your ICS/OT assets by exact version, with AI analysis, NERC CIP mapping, and vendor PSIRT contacts.

Create a free account →