CVE-2025-26659 Overview
CVE-2025-26659 is a DOM-based Cross-Site Scripting (XSS) vulnerability in SAP NetWeaver Application Server ABAP. The flaw stems from insufficient encoding of user-controlled inputs within the WEBGUI functionality. An unauthenticated attacker can craft a malicious web message that, when opened by a victim, triggers JavaScript execution in the victim's browser context. Successful exploitation results in limited confidentiality and integrity impact, with no impact on availability. The weakness is classified under CWE-79, Improper Neutralization of Input During Web Page Generation.
Critical Impact
Unauthenticated attackers can execute arbitrary JavaScript in a victim's browser session, compromising sensitive session data and manipulating rendered content within SAP WEBGUI.
Affected Products
- SAP NetWeaver Application Server ABAP
- SAP WEBGUI functionality
- SAP environments referenced under SAP Note #3552824
Discovery Timeline
- 2025-03-11 - CVE-2025-26659 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-26659
Vulnerability Analysis
The vulnerability exists in the WEBGUI component of SAP NetWeaver Application Server ABAP. The application fails to properly encode user-controlled input before it is written to the Document Object Model (DOM). Because encoding occurs client-side rather than server-side for this input path, attacker-controlled content flows into a JavaScript sink and is executed by the browser.
The attack requires no authentication but does require user interaction, such as clicking a crafted link or visiting an attacker-hosted page that sends a malicious web message. Once the payload reaches the vulnerable DOM sink, JavaScript executes in the origin of the SAP WEBGUI application. This grants the attacker access to session artifacts, page content, and any operations the user can perform in-browser. The scope is changed, meaning the injected script can act beyond the vulnerable component's original security boundary.
Root Cause
The root cause is missing or incomplete output encoding when handling user-controlled inputs delivered via web messages. Data received by client-side script is written into the DOM without sanitization, satisfying the classic conditions for DOM-based XSS described in CWE-79.
Attack Vector
Exploitation is network-based. An attacker delivers a crafted web message (for example, via window.postMessage or a malicious link) targeting the SAP WEBGUI page. When the victim's browser processes the message, the unsanitized payload is inserted into a DOM sink and evaluated as script. No prior credentials are required, but victim interaction is necessary to trigger the vulnerable code path. See SAP Note #3552824 for vendor-specific technical details.
Detection Methods for CVE-2025-26659
Indicators of Compromise
- Browser or proxy logs showing unexpected postMessage events targeting SAP WEBGUI origins with script-like payloads (<script>, javascript:, onerror=).
- SAP WEBGUI URLs containing encoded HTML fragments, event handlers, or JavaScript expressions in query parameters or fragments.
- Outbound requests from SAP WEBGUI users to unfamiliar domains immediately after opening an external link.
Detection Strategies
- Inspect web proxy and WAF logs for XSS payload signatures in traffic destined to SAP NetWeaver hosts.
- Enable Content Security Policy (CSP) violation reporting on SAP web frontends to surface inline script attempts.
- Correlate SAP audit logs with endpoint browser telemetry to identify suspicious cross-origin navigations preceding WEBGUI activity.
Monitoring Recommendations
- Monitor SAP Security Audit Log (SM19/SM20) for anomalous WEBGUI session activity following user clicks on external URLs.
- Alert on browser-side execution of unexpected scripts within *.sap.corp or equivalent SAP application domains.
- Track patch compliance for SAP NetWeaver ABAP systems against advisories listed on the SAP Security Patch Day portal.
How to Mitigate CVE-2025-26659
Immediate Actions Required
- Apply the SAP-provided fix documented in SAP Note #3552824 to all affected SAP NetWeaver Application Server ABAP systems.
- Restrict direct internet exposure of SAP WEBGUI endpoints and place them behind authenticated reverse proxies or VPN.
- Educate SAP users to avoid clicking untrusted links that redirect into SAP WEBGUI sessions.
Patch Information
SAP released a corrective patch published under SAP Security Patch Day. Administrators should reference SAP Note #3552824 for the exact support package or kernel patch level required for their SAP NetWeaver ABAP release. Consult the SAP Security Patch Day portal to align remediation with the broader monthly advisory cycle.
Workarounds
- Deploy a Web Application Firewall (WAF) rule set that filters XSS payload patterns targeting SAP WEBGUI URLs.
- Enforce a strict Content Security Policy on SAP web frontends to block inline script execution and untrusted script sources.
- Disable or restrict WEBGUI access for user populations that do not require it until patching is complete.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
