CVE-2026-34558

Vulnerability: Stored DOM XSS via Methods Management Fields (Global Persistent Payload Execution)

• Stored Cross-Site Scripting via Unsanitized Method Creation and Management Inputs
• Automatic Execution Across All Pages Where Method Is Rendered in Navigation

Description

The application fails to properly sanitize user-controlled input within the Methods Management functionality when creating or managing application methods/pages. Multiple input fields accept attacker-controlled JavaScript payloads that are stored server-side without sanitization or output encoding.

These stored values are later rendered directly into administrative interfaces and global navigation components without proper encoding, resulting in Stored DOM-Based Cross-Site Scripting (XSS).

Critically, because created methods are automatically rendered inside the system’s navigation/menu structure, the injected payload executes globally, meaning every page visited where the malicious method appears in the menu triggers the XSS payload automatically.

This significantly increases severity, as exploitation is not limited to a single view, it becomes a platform-wide persistent execution point.

Affected Functionality

• Methods creation functionality
• Methods management and listing functionality
• Administrative navigation rendering
• Permission-related UI rendering
• Global sidebar / menu rendering
• Storage and retrieval of method-related data

Affected Fields

The following fields accept unsanitized input and allow persistent JavaScript injection:

• Page Name
• Description
• Controller
• Method Name
• Seflink
• Page Order
• Symbol (FontAwesome 5)
• Permissions
• Parent Page
• Module

Attack Scenario

1. An attacker creates or edits a method.
2. The attacker injects a malicious XSS payload into any vulnerable field (e.g., Page Name).
3. The application stores the payload without sanitization or encoding.
4. The method is automatically rendered inside the application’s navigation/menu.
5. Every time any user visits any page where the menu is displayed, the malicious JavaScript executes automatically.

Because the navigation is globally rendered across backend pages, the XSS triggers on nearly every administrative page visit.

Steps To Reproduce (POC)

1. Navigate to Methods Management → Create Method
2. Insert the following payload into Page Name (or any vulnerable field):
   <img src=x onerror=alert(document.domain)>
3. Save the method
4. Navigate to any backend page
5. Observe the payload executing automatically wherever the malicious method appears in the menu
6. The XSS triggers across all pages where the navigation is rendered.

Ready Video POC:

https://mega.nz/file/CFsiQAJS#cBSF2lCMD7YNZEKYEjw3T8YturY92oBvrdRQ08gmw2A

• Persistent Stored DOM XSS
• Automatic execution across multiple application pages
• Execution of arbitrary JavaScript in victims’ browsers
• Privilege escalation when viewed by administrators
• Full administrator account takeover
• Full account takeover across all roles
• Session hijacking
• CSRF token theft
• Complete compromise of the entire application

This vulnerability is highly severe due to:

• Persistent storage
• Global rendering surface
• Automatic execution without user interaction
• High likelihood of administrator exposure

Endpoints:

• /backend/methods/
• /backend/methods/create

Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.

CVE-2026-34558 has a CVSS score of 9.1 (Critical). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.31.0.0); upgrading removes the vulnerable code path.

Kodem intelligence

• Never use .html(), innerHTML, or equivalent unsafe DOM sinks with untrusted data
• Implement strict output encoding (HTML entity encoding) before rendering user input
• Apply server-side input validation and sanitization
• Use contextual escaping depending on rendering context (HTML, attribute, JS, URL)
• Implement a strong Content Security Policy (CSP)
• Set cookies with HttpOnly, Secure, and SameSite flags
• Perform security review of all navigation rendering logic

Failure to properly encode and sanitize user-controlled method fields results in full application compromise through persistent global XSS.

1. What is CVE-2026-34558? CVE-2026-34558 is a critical-severity cross-site scripting (XSS) vulnerability in ci4-cms-erp/ci4ms (composer), affecting versions <= 0.28.6.0. It is fixed in 0.31.0.0. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
2. How severe is CVE-2026-34558? CVE-2026-34558 has a CVSS score of 9.1 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of ci4-cms-erp/ci4ms are affected by CVE-2026-34558? ci4-cms-erp/ci4ms (composer) versions <= 0.28.6.0 is affected.
4. Is there a fix for CVE-2026-34558? Yes. CVE-2026-34558 is fixed in 0.31.0.0. Upgrade to this version or later.
5. Is CVE-2026-34558 exploitable, and should I be worried? Whether CVE-2026-34558 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-34558 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-34558? Upgrade ci4-cms-erp/ci4ms to 0.31.0.0 or later.