CVE-2026-89107: SAP S/4HANA RCE Vulnerability

CVE-2026-89107 Overview

CVE-2026-89107 is an ABAP code injection vulnerability in the SAP S/4HANA Manage Substitution/Validation Rules application. The rule definition functionality uses a domain-specific scripting language that fails to sufficiently validate user-supplied input. An authenticated attacker holding specific business privileges can submit crafted input that the rule processing logic interprets as executable ABAP code. Successful exploitation grants arbitrary ABAP code execution and leads to full system compromise. The flaw is classified under CWE-94: Improper Control of Generation of Code.

Critical Impact
Authenticated attackers with low privileges can execute arbitrary ABAP code, resulting in full compromise of confidentiality, integrity, and availability of the affected S/4HANA system.

Affected Products

SAP S/4HANA — Manage Substitution/Validation Rules component
Refer to SAP Note #3805589 for the complete list of affected releases
Additional advisories available on the SAP Security Patch Day portal

Discovery Timeline

2026-10-13 - CVE-2026-89107 published to NVD
2026-10-15 - Last updated in NVD database

Technical Details for CVE-2026-89107

Vulnerability Analysis

The Manage Substitution/Validation Rules application in SAP S/4HANA allows business users to define substitution and validation rules through a domain-specific scripting language (DSL). The DSL expressions are compiled and evaluated by the rule processing engine at runtime. The engine does not enforce strict separation between data and code. Crafted input values submitted through the rule definition interface are interpreted as executable ABAP statements rather than being parsed as rule logic. This condition enables an attacker to inject code that runs with the privileges of the ABAP work process executing the rule. Because the scope changes during exploitation, impact extends beyond the vulnerable component to the broader system.

Root Cause

The root cause is insufficient input validation in the rule definition parser that handles DSL expressions. The parser passes attacker-controlled strings into an ABAP evaluation path without allow-listing permitted tokens or sanitizing script syntax. This is a classic code injection flaw [CWE-94] where user data crosses the trust boundary into the interpreter.

Attack Vector

Exploitation requires network access to the SAP S/4HANA application and an authenticated session with the business authorizations needed to create or modify substitution or validation rules. The attacker injects malicious DSL payloads that embed ABAP statements, saves the rule, and triggers rule evaluation. The injected ABAP executes within the SAP application server context, allowing read and modification of business data, creation of privileged users, and lateral movement to connected systems.

No public proof-of-concept code has been released. See SAP Note #3805589 for vendor technical details.

Detection Methods for CVE-2026-89107

Indicators of Compromise

Unexpected creation or modification of substitution and validation rules by business users outside standard change-management windows
ABAP short dumps or runtime errors (ST22) referencing dynamic code generation within rule processing modules
Creation of new ABAP users, role assignments, or RFC destinations with no corresponding change ticket
Outbound network connections initiated by the SAP work process to unfamiliar hosts

Detection Strategies

Enable SAP Security Audit Log (SM19/RSAU_CONFIG) and monitor events for rule configuration changes and dynamic ABAP execution
Review change documents for substitution and validation rule objects and correlate with authorized change requests
Baseline normal rule definition content and alert on expressions containing ABAP keywords such as CALL, GENERATE, or INSERT REPORT

Monitoring Recommendations

Forward SAP audit logs and system traces to a centralized SIEM for correlation with identity and network telemetry
Monitor privileged business roles that grant access to the Manage Substitution/Validation Rules Fiori application
Alert on anomalous OS-level process spawns from the SAP application server

How to Mitigate CVE-2026-89107

Immediate Actions Required

Apply the patch described in SAP Note #3805589 on all affected S/4HANA systems as a priority
Audit which users and roles currently hold authorizations to create or edit substitution and validation rules and remove unnecessary grants
Review existing substitution and validation rule definitions for suspicious DSL content before and after patching

Patch Information

SAP released the fix as part of SAP Security Patch Day. Download and installation instructions are available in SAP Note #3805589. Additional context is published on the SAP Security Patch Day page.

Workarounds

Restrict business authorizations for the Manage Substitution/Validation Rules application to a minimal set of trusted administrators until the patch is deployed
Enforce a four-eyes approval workflow for any rule creation or change in production
Increase monitoring of SAP audit logs for rule configuration activity during the exposure window

bash

# Reference only — consult SAP Note #3805589 for the authoritative procedure
# 1. Download the correction from SAP ONE Support Launchpad
# 2. Import the Support Package or SAP Note via SNOTE / SPAM
# 3. Validate authorization objects controlling rule maintenance
# 4. Re-run SAP Security Audit Log review (RSAU_READ_LOG)