CVE-2026-89107

Executive Summary

CVE-2026-89107 is a critical code injection vulnerability (CWE-94) in SAP S/4HANA's Manage Substitution/Validation Rules functionality, where insufficient input validation of user-supplied rule definitions allows crafted input to be interpreted as executable ABAP code. An authenticated attacker holding specific business privileges can inject and execute arbitrary ABAP code within the SAP application server context, resulting in full system compromise with high impact to confidentiality, integrity, and availability. With a CVSS score of 9.9 (network-exploitable, scope-changed), this vulnerability demands urgent remediation attention despite no public PoC or patch currently being available.

Technical Analysis

CVE-2026-89107 resides in the Manage Substitution/Validation Rules component of SAP S/4HANA, a core business configuration module that allows administrators and authorized users to define custom business rules governing financial and accounting document processing. These rules are authored using a domain-specific scripting language, which is designed to constrain user expressions to safe, non-executable business logic constructs.

The vulnerability stems from CWE-94 (Improper Control of Generation of Code / Code Injection). The rule definition functionality fails to sufficiently validate input before that input is processed by the underlying rule processing logic. Because the rule processing engine interprets the domain-specific scripting language on the ABAP application server, crafted input that escapes the intended script grammar can be rendered as executable ABAP code rather than remaining sandboxed as inert rule syntax.

The critical security boundary that is violated is the separation between the constrained domain-specific scripting language and native ABAP runtime execution. SAP's rule engines are expected to parse and evaluate rule definitions within a restricted interpreter that cannot invoke arbitrary ABAP statements, function modules, or system operations. When input validation is insufficient, an attacker with the business rights to author substitution or validation rules can smuggle ABAP code that the rule processor then executes with the privileges of the rule execution context.

The CVSS vector confirms the severity characteristics. Network attack vector (AV:N) indicates the rule management interface is remotely reachable. Low attack complexity (AC:L) and no user interaction (UI:N) mean exploitation requires no special conditions beyond the attacker's existing access. The required privilege level (PR:L) reflects that the attacker must already hold specific business privileges to define rules. Notably, Scope is Changed (S:C), indicating that a successful exploit can affect resources beyond the vulnerable component's authorization scope — consistent with code executing under the SAP application server's security context rather than the attacker's original privilege set. All impact metrics (C:H/I:H/A:H) are high.

No public proof-of-concept, Nuclei template, or exploit code exists at the time of writing, and the CNA title field is empty, so the precise affected S/4HANA release ranges, the exact scripting language grammar, and the specific validation routine at fault cannot be confirmed from the available intelligence. The vulnerability class — injection of native code through an interpreted rule language — is nonetheless well-established in enterprise ERP platforms, where rule engines frequently bridge a scripting facade to a powerful server-side execution engine.

Exploitation Scenarios

The attack chain for CVE-2026-89107 is inferred from the vulnerability class (CWE-94) and the NVD description; no public PoC is available.

1. Reconnaissance / target identification. The attacker identifies an SAP S/4HANA system exposing the Manage Substitution/Validation Rules management function. Because the vulnerability requires authentication, the attacker either possesses legitimate credentials with the business privileges needed to define rules, or has obtained such credentials through prior compromise, credential reuse, or insider access. The attacker confirms access to the rule definition interface.

2. Triggering the flaw class. Using the rule definition functionality, the attacker submits a crafted rule expression via the domain-specific scripting language interface. The input is designed to break out of the intended script grammar — exploiting the insufficient validation — so that the rule processing logic parses a portion of the input as executable ABAP code rather than constrained script syntax. The mechanism is code injection through improper neutralization of input used to generate code.

3. Payload / execution method (vulnerability-class level). When the substitution or validation rule is processed — either on submission, on activation, or when a governed business transaction is executed — the injected ABAP is interpreted and run by the rule processing logic on the SAP application server. Because no specific function names, parameters, or endpoints are disclosed in the available intelligence, the exact injection syntax and execution trigger cannot be stated without fabrication; the defining characteristic is that crafted rule input becomes executable ABAP.

4. Post-exploitation impact. Successful execution yields arbitrary ABAP code execution in the SAP system context. Given the Scope:Changed rating, execution occurs beyond the attacker's original authorization boundary. This enables full compromise of the affected system: access to and modification of business data (high integrity impact), exfiltration of sensitive records (high confidentiality impact), and disruption of critical business processes (high availability impact). Because ABAP execution can reach database operations and system utilities available to the application server, the blast radius extends to any data or function the executing context can reach.

Impact Assessment

CVE-2026-89107 carries a CVSS v3.1 base score of 9.9, placing it in the Critical severity band. The impact assessment is driven by the scope-changed, fully compromised CIA triad outcome:

• Confidentiality (High): Execution of arbitrary ABAP code grants access to business documents, financial records, master data, and potentially credentials or configuration secrets accessible to the application server.
• Integrity (High): An attacker can alter business rules, financial postings, substitution/validation outcomes, and other SAP-managed data, undermining the trustworthiness of the ERP system of record.
• Availability (High): Malicious ABAP can disrupt or halt business processes, degrade the application server, or trigger denial-of-service conditions affecting critical S/4HANA workloads.
• Scope (Changed): The exploit affects resources beyond the vulnerable component's security scope, meaning the compromise is not contained to the rule management function. Enterprise resource planning systems of record like S/4HANA are high-value targets; full compromise produces significant regulatory, financial, and operational risk. The required privilege (PR:L) somewhat narrows the initial attack surface to authenticated users with specific business rights, but any such user — or an attacker who obtains those rights — can escalate to complete system control.

Detection Guidance

Sigma Rule

title: SAP S/4HANA Rule Definition Code Injection Attempt (CVE-2026-89107)
id: 8f3a1c2e-4b7d-4e91-9a5c-2d6e7f8a1b3c
status: experimental
description: Detects submission of crafted rule definitions in SAP S/4HANA Manage Substitution/Validation Rules that may inject executable ABAP code.
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-89107
author: valtersit.com
date: 2026/01/01
logsource:
  product: sap
  service: s4hana_rule_engine
detection:
  keywords:
    - 'INSERT'
    - 'CALL FUNCTION'
    - 'SUBMIT'
    - 'EXEC'
    - 'ENDEXEC'
    - 'ABAP'
  selection_rule_action:
    action|contains:
      - 'substitution_rule'
      - 'validation_rule'
  condition: selection_rule_action and keywords
falsepositives:
  - Legitimate administrative rule authoring containing reserved-word lookalikes
level: high

YARA Rule

rule CVE_2026_89107_SAP_Rule_Injection
{
    meta:
        description = "Detects ABAP code-injection payloads in SAP S/4HANA rule definitions"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-89107"
        cve = "CVE-2026-89107"
        author = "valtersit.com"
    strings:
        $abap1 = "CALL FUNCTION" nocase
        $abap2 = "INSERT REPORT" nocase
        $abap3 = "SUBMIT " nocase
        $abap4 = "ENDEXEC" nocase
        $abap5 = "EXEC SQL" nocase
        $rule = "substitution" nocase
    condition:
        filesize < 1MB and ($rule and any of ($abap*))
}

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-89107 SAP S/4HANA Rule Injection ABAP Payload"; flow:established,to_server; http.method; content:"POST"; http.uri; content:"substitution"; nocase; http.request_body; content:"CALL FUNCTION"; nocase; http.request_body; content:"ENDEXEC"; nocase; reference:cve,2026-89107; classtype:web-application-attack; sid:202689107; rev:1;)

Elastic Detection

sequence by user.name, source.ip with maxspan=5m
  [http where http.request.method == "POST" and
   string(network.protocol) == "http" and
   wildcard(url.path, "*substitution*") and
   wildcard(http.request.body, "*CALL FUNCTION*")]

Splunk SPL Query

index=sap sourcetype=sap:abap OR sourcetype=sap:web
| search (url="*substitution*" OR url="*validation*" OR rule_action="*rule*")
| where match(request_body, "(?i)(CALL\s+FUNCTION|INSERT\s+REPORT|ENDEXEC|SUBMIT\s+|EXEC\s+SQL)")
| stats count values(request_body) as payloads by user, src_ip, url
| where count > 0

Wazuh OSSEC Rule

<group name="sap,s4hana">
  <rule id="100891" level="12">
    <decoded_as>json</decoded_as>
    <field name="rule_action">substitution_rule|validation_rule</field>
    <regex type="pcre2">(?i)(CALL\s+FUNCTION|INSERT\s+REPORT|ENDEXEC|SUBMIT\s+|EXEC\s+SQL)</regex>
    <description>CVE-2026-89107: Possible ABAP code injection via SAP S/4HANA rule definition</description>
    <mitre>
      <id>T1190</id>
    </mitre>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 (UNPATCHED — no patch evidence from any tracked source).

1. Immediate mitigations. Given no patch is available, restrict the assignment of business privileges that allow authoring or activating substitution and validation rules to the smallest possible set of trusted users. Audit existing rule definitions for suspicious or malformed content and remove any untrusted entries. Where feasible, place the rule management interface behind network access controls, VPN, or reverse proxies with strict allowlists, and enforce strong authentication (MFA) for all accounts with rule-authoring rights. Enable verbose SAP security audit logging covering rule changes and rule execution.

2. Patch/upgrade steps. Monitor SAP Security Notes and the SAP Support Portal for a security note addressing CVE-2026-89107, and apply the corresponding kernel or component patch as soon as it is released. Track SAP's official advisories through the SAP Trust Center and apply the fix through SAP Note implementation. Until a patch is published, treat the system as unpatched and rely on compensating controls.

3. Long-term hardening. Adopt a defense-in-depth posture for ERP rule engines: segregate rule-authoring privileges from general business users, implement strict input validation and output encoding at the platform layer once vendor guidance is available, monitor rule engine inputs for scripting-language escape patterns, and include ABAP code-injection payload signatures in SIEM/IDS detection pipelines. Regularly review custom rule definitions and maintain change-control and least-privilege governance over the Manage Substitution/Validation Rules functionality.

References

• NVD — CVE-2026-89107: https://nvd.nist.gov/vuln/detail/CVE-2026-89107
• CWE-94 — Improper Control of Generation of Code ('Code Injection'): https://cwe.mitre.org/data/definitions/94.html
• SAP Trust Center / SAP Security Notes (monitor for advisory addressing CVE-2026-89107): https://www.sap.com/trust-center.html
• MITRE ATT&CK T1190 — Exploit Public-Facing Application: https://attack.mitre.org/techniques/T1190/
• CISA Known Exploited Vulnerabilities Catalog (currently no KEV entry for CVE-2026-89107 at time of writing): https://www.cisa.gov/known-exploited-vulnerabilities-catalog No threat actor campaigns or exploit-in-the-wild evidence are associated with CVE-2026-89107 in the available intelligence.