CVE-2025-27431: SAP NetWeaver Stored XSS Vulnerability

CVE-2025-27431 Overview

CVE-2025-27431 is a stored Cross-Site Scripting (XSS) vulnerability in the user management functionality of SAP NetWeaver Application Server Java. An authenticated attacker with low privileges can inject a malicious script payload that persists in server-side storage. The payload executes in the browser of any user who subsequently accesses the affected functionality.

Successful exploitation enables information disclosure and unauthorized data modification within the victim's browser session. Availability is not affected. The vulnerability is tracked under CWE-79 (Improper Neutralization of Input During Web Page Generation).

Critical Impact
Authenticated attackers can persistently inject scripts into SAP NetWeaver AS Java user management, leading to session data theft and unauthorized actions performed under the identity of higher-privileged administrators.

Affected Products

SAP NetWeaver Application Server Java
User management functionality component
Refer to SAP Note #3567246 for the full list of impacted versions

Discovery Timeline

2025-03-11 - CVE-2025-27431 published to NVD as part of SAP Security Patch Day
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-27431

Vulnerability Analysis

The flaw resides in the user management module of SAP NetWeaver Application Server Java. The application accepts user-supplied input and renders it back into an administrative interface without sufficient output encoding or input sanitization. Because the injected content is stored server-side, the payload triggers every time a legitimate user loads the affected view.

The attack requires low privileges and user interaction, but the impact crosses a security scope. A low-privileged user can inject payloads that execute in the browser of higher-privileged administrators who access the same interface. This scope change amplifies the practical risk, since administrator sessions carry broader authorization within the SAP environment.

Impact is limited to confidentiality and integrity within the victim browser. Attackers can read session tokens, exfiltrate displayed data, or issue forged requests against SAP endpoints on behalf of the victim. Availability of the NetWeaver AS Java instance is unaffected.

Root Cause

The root cause is missing or incomplete output encoding when the user management interface renders attacker-controlled fields. Input that should be treated as data is instead interpreted by the browser as executable HTML or JavaScript, matching the classic [CWE-79] pattern.

Attack Vector

The attack vector is network-based over HTTP or HTTPS. An authenticated attacker submits a crafted value into a user management field. The payload is stored in SAP backend storage. When an administrator or other user opens the affected page, the browser parses and executes the injected script in the origin context of the SAP application.

No verified proof-of-concept exploit code is publicly available. Refer to the SAP Security Patch Day advisory for vendor-provided technical details.

Detection Methods for CVE-2025-27431

Indicators of Compromise

Unexpected HTML tags, <script> fragments, or JavaScript event handlers (onerror, onload) stored in user profile fields within the SAP NetWeaver AS Java user management database
Outbound HTTP requests from administrator browser sessions to unfamiliar external domains shortly after accessing user management pages
Session tokens or SAP administrative cookies appearing in web server referrer logs or third-party telemetry

Detection Strategies

Review SAP NetWeaver AS Java application logs for user management create and modify operations containing HTML control characters such as <, >, or javascript:
Deploy Content Security Policy (CSP) violation reporting on SAP administrative interfaces to surface unexpected inline script execution
Correlate administrator authentication events with anomalous downstream API calls that suggest browser-driven request forgery

Monitoring Recommendations

Ingest SAP NetWeaver AS Java HTTP access logs and security audit logs into a centralized SIEM for pattern matching against known XSS payload signatures
Alert on POST or PUT requests to user management endpoints that contain encoded script fragments such as %3Cscript%3E or <script>
Monitor privileged administrator accounts for unusual activity patterns following interaction with user management screens

How to Mitigate CVE-2025-27431

Immediate Actions Required

Apply the SAP-provided patch referenced in SAP Note #3567246 to all affected NetWeaver AS Java instances
Audit existing user management records for stored payloads containing HTML or JavaScript syntax and remediate any injected content
Restrict access to user management functionality to the smallest possible administrator group until patching is complete

Patch Information

SAP released the fix as part of its monthly Security Patch Day. Customers should consult SAP Note #3567246 for version-specific patch information and installation guidance. Additional context is available through the SAP Security Patch Day portal.

Workarounds

Enforce a strict Content Security Policy on SAP administrative interfaces to block inline script execution
Route access to the NetWeaver AS Java administration console through a web application firewall configured with XSS payload signatures
Require administrators to use dedicated, hardened browser profiles when interacting with SAP user management functionality

bash

# Example CSP header to reduce XSS impact on SAP admin interfaces
# Applied at the reverse proxy in front of NetWeaver AS Java
add_header Content-Security-Policy "default-src 'self'; script-src 'self'; object-src 'none'; base-uri 'self'; frame-ancestors 'self'" always;