CVE-2026-27599 — ci4ms
MEDIUMCVE-2026-27599 is a medium-severity (CVSS 4.7) Cross-site Scripting (XSS) vulnerability in ci4-cms-erp/ci4ms. A fix is available for ci4-cms-erp/ci4ms — see the affected versions and patch details below.
CI4MS: System Settings (Mail Settings) Full Platform Compromise & Full Account Takeover for All-Roles & Privilege-Escalation via Stored DOM XSS
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-27599.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
ci4-cms-erp/ci4msReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
Summary
Vulnerability: Stored DOM XSS via System Settings – Mail Settings (Same-Page Attribute Breakout & Persistent Payload Injection)
- Stored Cross-Site Scripting via Unsanitized Mail Settings Configuration Fields
Description
The application fails to properly sanitize user-controlled input within System Settings – Mail Settings. Several configuration fields, including Mail Server, Mail Port, Email Address, Email Password, Mail Protocol, and TLS settings, accept attacker-controlled input that is stored server-side and later rendered without proper output encoding.
Unlike public-facing XSS that executes on landing pages, this vulnerability executes immediately on the same settings page. The injected payload breaks out of the HTML attribute context and is interpreted by the browser when rendered, resulting in same-page DOM-based XSS.
This represents different functionality and a separate vulnerability from landing-page injection.
Example Affected Fields
- Mail Server:
test - Mail Port:
465 - Email Address:
[email protected] - Email Password: (any input)
- Mail Protocol:
SMTP - Domain:
[email protected]
Affected Functionality
- System Settings – Mail Settings configuration
- Same-page rendering of user-controlled input fields
- DOM attribute injection within form inputs
- Storage and retrieval of mail configuration values
Attack Scenario
- An attacker injects a malicious JavaScript payload into one or more Mail Settings fields.
- The payload breaks out of the HTML attribute context.
- The application stores and re-renders the payload without sanitization or encoding.
- The payload executes immediately on the same settings page.
- The script executes in the browser context of the authenticated user managing Mail Settings.
Impact
- Persistent Stored XSS
- Immediate Same-Page DOM XSS execution
- Execution of arbitrary JavaScript in victims’ browsers
- Administrative privilege escalation
- Full administrator account takeover
- Full account takeover across all roles
- Full compromise of the entire platform
Endpoints:
/backend/settings/(Mail Settings)
Steps To Reproduce (POC)
- Navigate to System Settings -> Mail Settings
- Insert the following XSS payload into any Mail Settings field:
test"><img src=1 onerror=alert()>" class="form-control" placeholder="Name" required> - Save the settings
- Observe that the payload breaks out of the input attribute context
- The XSS executes immediately on the same page
Remediation
- Never use .html() or any innerHTML-style sinks for user-controlled input in PHP or JavaScript.
- Apply proper HTML encoding and input sanitization for all configuration fields.
- Enforce CSP, HttpOnly, SameSite, and Secure flags for cookies to reduce the severity of XSS and potential CSRF escalation.
- Audit all other system settings fields for similar attribute injection vulnerabilities.
Ready Video POC:
https://mega.nz/file/KRNhUI6Q#NGC3Bow3RlnmdU1H2bGu1BGbpfIc-awi6IlvTp08V1s
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | ci4-cms-erp/ci4ms | all versions | 0.31.0.0composer require ci4-cms-erp/ci4ms:^0.31.0.0 |
Affected Products
ci4msci4-cms-erpDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for ci4-cms-erp/ci4ms, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update ci4-cms-erp/ci4ms to 0.31.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-27599 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
Frequently Asked Questions
Is CVE-2026-27599 in your dependencies?
Find it across Packagist, including transitive dependencies.