CVE-2026-34571 — ci4-cms-erp/ci4ms
CRITICALCVE-2026-34571 is a critical-severity (CVSS 9.9) 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: Stored Cross‑Site Scripting (Stored XSS) in Backend User Management Allows Session Hijacking and Full Administrative Account Compromise
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.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-34571.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-34571 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,156 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
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
A critical Stored Cross-Site Scripting (Stored XSS) vulnerability exists in the backend user management functionality. The application fails to properly sanitize user-controlled input before rendering it in the administrative interface, allowing attackers to inject persistent JavaScript code. This results in automatic execution whenever backend users access the affected page, enabling session hijacking, privilege escalation, and full administrative account compromise.
Details
The vulnerability resides in the backend user creation feature accessible via:
/backend/users
User-supplied input in the name and surname fields is stored without proper validation or sanitization. When this data is later rendered in the backend users listing page, it is injected directly into the HTML without output encoding.
Because of this, attackers can embed malicious JavaScript payloads that execute in the context of authenticated backend users.
This indicates missing contextual output escaping (e.g., HTML encoding) and insufficient input sanitization, leading to persistent script execution.
The vulnerability is particularly severe because:
- The payload is stored in the database (persistent XSS).
- The script executes automatically on page load.
- The affected page appears to be an administrative/backend interface, increasing the risk of privilege escalation.
PoC
Steps to reproduce:
- Navigate to:
http://localhost:8080/backend/users
-
Click Add New User.
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Create a new user.
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In the name and surname fields, insert the following payload:
adnan"><img src=1 onerror=alert(document.cookie)><<e>img src=1 onerror=alert(document.cookie)>
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Save the user.
-
After saving, a popup displaying cookies will appear, demonstrating JavaScript execution.
-
Revisit:
http://localhost:8080/backend/users
- The popup automatically triggers again, confirming that the malicious script is stored and executed persistently. <img width="1534" height="834" alt="image" src="https://github.com/user-attachments/assets/83f3d124-cf2e-472d-87cc-8c668ea81cba" />
Impact
Severity: Critical
This vulnerability enables:
- Persistent execution of attacker-controlled JavaScript in privileged backend contexts.
- Theft of session cookies, potentially leading to full account takeover.
- Unauthorized actions performed on behalf of administrators (CSRF-like behavior via XSS).
- Privilege escalation if a high-privilege user views the page.
- Injection of keyloggers, credential harvesting scripts, or malicious redirects.
- Full compromise of backend administrative functionality depending on role permissions.
Since the payload executes automatically without user interaction once stored, exploitation requires minimal effort and can impact all backend users.
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 |
Detection & 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-2026-34571 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-34571 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-34571. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-34571 in your dependencies?
O3 Security finds CVE-2026-34571 across Packagist dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.