XML Signature Wrapping Vulnerability in SAP NetWeaver ABAP Enables Identity Tampering and Unauthorized Access (CVE-2026-23687)
Vulnerability Overview
SAP has disclosed a high-severity XML Signature Wrapping vulnerability in SAP NetWeaver Application Server ABAP and ABAP Platform as part of its February 2026 Security Patch Day. Tracked as CVE-2026-23687 with a CVSS score of 8.8, this flaw allows an authenticated attacker with normal (low) privileges to manipulate signed XML documents and bypass identity verification controls — potentially gaining unauthorized access to sensitive user data and disrupting normal system operations.
The vulnerability targets the XML signature verification process within the ABAP platform. An attacker with valid SAP credentials can obtain a legitimately signed message, modify its contents, and resubmit the tampered document to the verifier. Because the signature validation logic fails to properly detect the manipulation, the system accepts the forged XML as authentic — effectively allowing the attacker to impersonate other users or escalate their own privileges.
SAP NetWeaver ABAP is one of the most widely deployed enterprise application platforms in the world. It serves as the backbone for countless critical business processes across finance, manufacturing, retail, healthcare, and government sectors. The combination of network-based attack vector, low attack complexity, and high impact across confidentiality, integrity, and availability makes this vulnerability a serious concern for any organization running affected SAP infrastructure.
Technical Details
CVE-2026-23687 exploits a weakness in how the ABAP platform handles XML digital signatures. XML Signature Wrapping (XSW) attacks work by restructuring a signed XML document so that the signature remains mathematically valid, but the verifier processes attacker-controlled content instead of the originally signed data. This is a well-known class of vulnerability that has historically affected SAML-based authentication systems, web services, and identity federation protocols.
In this case, an attacker who holds valid SAP credentials — even low-privileged ones — can intercept or obtain a legitimately signed XML message and restructure it to inject tampered identity information. When the modified document is sent to the verification endpoint, the system accepts it, potentially granting the attacker access under a different identity or with elevated permissions.
Successful exploitation could result in:
- Identity spoofing — Tampered identity information is accepted by the verifier, allowing the attacker to act as another user
- Unauthorized data access — Sensitive user data and business-critical information becomes accessible
- Lateral movement — If trusted downstream components rely on the compromised identity data, the attacker may pivot within the SAP landscape
- Service disruption — Manipulation of identity claims can disrupt normal system operations and business processes
Affected Versions
The vulnerability affects a broad range of SAP_BASIS versions spanning legacy and current releases:
Patch & Remediation
February 2026 Patch Day Context
CVE-2026-23687 is one of several high-impact vulnerabilities addressed in SAP's February 2026 Patch Day, which included 29 new and updated security notes in total. Other notable patches released alongside this advisory include:
- SAP Security Note #3697099 (CVSS 9.9) — Critical Code Injection in SAP CRM and S/4HANA allowing execution of arbitrary SQL statements
- SAP Security Note #3674774 (CVSS 9.6) — Missing Authorization Check in SAP NetWeaver AS ABAP enabling unauthorized background RFC calls
- SAP Security Note #3705882 (CVSS 7.7) — Information Disclosure in SAP Solution Tools Plug-In (ST-PI)
- SAP Security Note #3692405 (CVSS 7.4) — SSL Trust Validation Bypass in SAP Commerce Cloud
- SAP Security Note #3674246 (CVSS 7.3) — Open Redirect in SAP BusinessObjects BI Platform
Organizations running SAP environments should review the full February 2026 Patch Day bulletin and prioritize remediation based on their specific deployment landscape.
Detection Indicators
- Successful processing of tampered signed XML documents where identity attributes differ from signed claims
- Anomalous authentication events where user identity does not match the expected signed assertion
- Repeated signature verification faults followed by privileged data access or system calls
- Unexpected changes in user session context or privilege levels after XML-based authentication
Recommendations
- Apply SAP Security Note #3697567 immediately. Test in a staging environment before production rollout. The available workaround does not cover all signed XML usage scenarios.
- Restrict network exposure. Limit access to ABAP signing and verification endpoints. Enforce least privilege and network segmentation for SAP interfaces.
- Audit identity and authentication logs. Look for mismatches between signed data and identity claims, unusual privilege escalations, or unexpected user context switches.
- Review the full February 2026 Patch Day. Multiple critical and high-severity vulnerabilities were patched — prioritize based on your SAP landscape exposure.
- Plan for downtime. Schedule remediation with a defined maintenance window and verify rollback procedures before deploying patches to production.
){kind=link}