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YOOtheme Zoo EUVDEUVD-2026-62434

| CVE-2026-74803 CRITICAL
Unrestricted Upload of File with Dangerous Type (CWE-434)
2026-08-19 Joomla GHSA-c2jh-c375-pjcv
10.0
CVSS 4.0 · Vendor: Joomla
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Identify Joomla site with Zoo image element
  2. Delivery
    Craft upload POST with image/* Content-Type header
  3. Exploit
    Bypass MIME check, store PHP web shell
  4. Execution
    Request uploaded shell URL
  5. Impact
    Execute commands, full host compromise

Vulnerability Assessment

Weakness
CWE
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.

Exploitation Conditions

The vulnerable path is the Zoo 'image element' upload feature: exploitation requires that a Zoo image element / upload endpoint be reachable by the attacker and accept submissions without prior authentication, and that the attacker set the HTTP Content-Type header to a value within the image MIME group (e.g. image/jpeg, image/png) while sending non-image executable content. The bypass works because only the client-supplied Content-Type is validated, not file content or extension. Limiting factors that reduce real-world exposure: the target Joomla site must actually expose a Zoo image upload element to unauthenticated users, the upload directory must permit server-side script execution for code execution to follow, and the site must be running Zoo below 4.1.64. Where the upload form is behind authentication or the storage directory forbids script execution, impact is reduced.

Impact

All available signals point to genuine high priority: the CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:N) indicates network-reachable, low-complexity exploitation with no privileges and no user interaction, and the impact metrics (VC:H/VI:H/VA:H, SC:H/SI:H/SA:H) reflect that a successful upload of executable code yields full compromise of the host. The base score of 10.0 is consistent with unauthenticated remote code execution via web-shell upload. Countervailing signals: this CVE is NOT in CISA KEV, and there is no evidence of public exploit code (POC=no) or active exploitation, so the practical risk today is driven by ease of weaponization rather than confirmed in-the-wild activity - CWE-434 Content-Type-only bypasses are trivial to reproduce, so exploitation should be treated as imminent once the flaw is public. No EPSS score was provided in the input, so probabilistic exploitation likelihood cannot be quantified here. The description ('image element accepts arbitrary files') strongly corroborates the network, unauthenticated CVSS profile with no obvious contradiction.

Exploit ScenarioDerived

A remote, unauthenticated attacker locates a Joomla site running a vulnerable Zoo image element and submits a POST request uploading a PHP web shell while setting the request Content-Type header to an image type such as image/jpeg. The server accepts the file based solely on that header, storing the executable script in a web-accessible directory; the attacker then requests the uploaded file's URL to execute commands and gain a foothold. No public exploit code is currently identified, but the technique is trivial to build.

Act Now Prioritize within 24-48h. Why: CRITICAL severity.
No patch listed yet 0.3% exploitation probability (EPSS)

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AnalysisAIv1 – Aug 19, 2026

Unauthenticated arbitrary file upload in the YOOtheme Zoo content-builder extension for Joomla (versions before 4.1.64) allows remote attackers to upload arbitrary files, including web shells, because the image element only validates the client-supplied Content-Type header against the image MIME group rather than the actual file contents or extension. Rated CVSS 4.0 base 10.0 with full confidentiality, integrity, and availability impact plus scope change, this is a critical pre-authentication flaw. No public exploit identified at time of analysis, and it is not listed in CISA KEV.

RemediationAI

Vendor-released patch: 4.1.64 - upgrade the Zoo extension to version 4.1.64 or later, which is the primary and complete fix. Consult the vendor at https://www.yootheme.com/ for the release notes and download. Until the update can be applied, apply compensating controls: restrict or disable public/unauthenticated access to the Zoo image upload endpoint (for example require authentication or IP-allowlist the submission page), which trades off any legitimate anonymous content submission; add a WAF or web-server rule to reject uploads whose stored content does not match validated image magic bytes and to block requests attempting to store .php/.phtml/.php5/.phar files in upload directories; and configure the web server to disable script execution (e.g. remove PHP handler / set Options -ExecCGI) within Zoo's media/upload directories so any uploaded file cannot be executed, with the side effect that no server-side code in those paths will run. Verify no web shells were already placed before patching.

Affected VersionsENISA

Zoo extension for Joomla 1.0.0-4.1.63

Affected Packages

euvd zoo_extension_for_joomla no fix

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in euvd

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

Technical ContextAI · show details

Zoo is a widely used content and application builder for the Joomla CMS developed by yootheme.com (CPE: cpe:2.3:a:yootheme.com:zoo_extension_for_joomla). The vulnerability is a classic CWE-434 (Unrestricted Upload of File with Dangerous Type): the extension's image element upload handler trusts the attacker-controlled HTTP Content-Type request header to decide whether a file is a permitted image. Because MIME type in the Content-Type header is entirely client-supplied, an attacker can label a PHP script (or other executable server-side content) with a value in the image/* group (e.g. image/jpeg) and bypass the type check, since there is no server-side magic-byte inspection, extension allow-listing, or re-encoding of the uploaded content.

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Severity by source

Vendor (Joomla) PRIMARY 10.0 CRITICAL
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
vuln.today AI 10.0 CRITICAL

Remote unauthenticated upload with no user interaction (AV:N/AC:L/PR:N/UI:N); uploaded code executes on the web host beyond the vulnerable component so scope changes (S:C) with full C/I/A impact.

3.1 AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

Primary rating from Vendor (Joomla).

CVSS VectorVendor: Joomla

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
None
Privileges Required
None
User Interaction
None
Vulnerable system: Confidentiality
High
Vulnerable system: Integrity
High
Vulnerable system: Availability
High
Subsequent system: Confidentiality
High
Subsequent system: Integrity
High
Subsequent system: Availability
High

DescriptionCVE.org

Joomla Extension - yootheme.com - Unauthenticated arbitrary file upload in Zoo < 4.1.64 - The image element accepts arbitrary files when the client-supplied Content-Type falls within the image MIME group.

Executive ViewAI

Why It Matters

YOOtheme Zoo extension for Joomla versions prior to 4.1.64 contains a critical unauthenticated file upload vulnerability enabling remote code execution via web shell deployment. Although no public exploit identified at time of analysis, the ease of exploitation and perfect CVSS 10.0 score represent immediate organizational risk; any compromised instance could result in complete system takeover, data theft, or ransomware deployment.

Business Impact: Severe
Compensating Controls

Until vendor patch released: disable Zoo extension if operationally feasible; implement role-based access controls restricting upload functionality to trusted administrators only; deploy WAF rules blocking uploads with executable extensions (.php, .jsp, .asp, .exe) or suspicious MIME type signatures; establish continuous monitoring of upload directories and web server access logs for exploitation attempts; isolate affected systems on restricted network segments; conduct periodic file integrity monitoring of upload directories.

Threat Intelligence Overview

EPSS Score
0.3%
Top 76% exploitable
Prevalence
Medium
popular Joomla content-builder extension, but Joomla itself is a minority CMS
Data Quality
5 sources
Confidence: Medium

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 CRITICAL
CISA KEV No
Public POC No
EPSS 0.3%
Patch available No
Active threat No
Deciding rule
CRITICAL severity
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
Out-of-Cycle
Exploitation
None
System Exposure· derived
Open
Automatable
Yes
Human Impact
Very High
Technical Impact
Total

Priority Score

50
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +50
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

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

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