CVE-2026-66766 in S4HANA
Summary
by MITRE • 08/25/2026
SAP S/4HANA (Private Cloud) uses a third-party component that contains a Regular Expression Denial of Service (ReDoS) vulnerability. An unauthenticated attacker could supply specially crafted input that triggers excessive processing within the affected functionality. Successful exploitation could exhaust system resources and make the service unavailable, resulting in a high impact on availability. There is no impact on confidentiality and integrity.
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Analysis
by VulDB Data Team • 08/25/2026
The identified security issue resides within SAP S/4HANA Private Cloud Edition and stems from a vulnerability in a third-party component utilized by the platform. This specific flaw manifests as a Regular Expression Denial of Service, commonly referred to as ReDoS. Unlike vulnerabilities that compromise data confidentiality or system integrity, this defect is strictly an availability concern. The root cause lies in the implementation of regular expression patterns within the affected functionality, which exhibit catastrophic backtracking behavior when processing certain inputs. This architectural weakness allows for significant computational overhead during string matching operations, creating a pathway for resource exhaustion attacks without requiring any form of authentication or prior access to the system.
From a technical perspective, Regular Expression Denial of Service vulnerabilities arise when regex engines employ algorithms that can be forced into exponential time complexity relative to input length. In this instance, an unauthenticated attacker is able to supply specially crafted input strings designed to trigger these inefficient processing paths. The regular expression engine attempts to evaluate multiple potential matches through backtracking, a process where the engine tries different combinations of characters in the pattern against the input string. When the regex contains ambiguous quantifiers or nested repetitions without proper anchoring or optimization, the number of steps required to determine a match can grow exponentially rather than linearly. This results in the CPU and memory resources being consumed at an alarming rate as the system attempts to resolve the complex matching logic embedded within the third-party component.
The operational impact of this vulnerability is severe regarding service availability but neutral concerning other security pillars. Successful exploitation allows an attacker to exhaust critical system resources, effectively rendering the SAP S/4HANA Private Cloud instance unavailable to legitimate users and business processes. This denial of service condition can lead to significant downtime for enterprise operations that rely on the platform for mission-critical functions such as finance, supply chain management, or human resources processing. Because there is no impact on confidentiality, sensitive data remains secure from exposure during an attack. Similarly, integrity is unaffected, meaning the attacker cannot alter stored data or execute arbitrary code through this specific vector. The primary consequence is a disruption of service that requires administrative intervention to restore normal operations once the attack subsides or resources are reclaimed.
This vulnerability aligns with Common Weakness Enumeration identifier CWE-400, which describes Uncontrolled Resource Consumption, specifically under the sub-category of Regular Expression Denial of Service. In terms of offensive security frameworks, this exploit technique corresponds to MITRE ATT&CK tactic T1499, Endpoint Denial of Service, and more specifically aligns with techniques that leverage application layer vulnerabilities to degrade service quality. The lack of authentication requirement classifies it as a remote attack vector accessible from untrusted networks, increasing the risk surface significantly for cloud-hosted instances exposed to public internet traffic or partner integrations without sufficient perimeter filtering.
Mitigation strategies must focus on both immediate remediation and long-term architectural improvements. SAP has likely released patches addressing this specific third-party component vulnerability; therefore, applying the latest security updates provided by SAP is the primary corrective action. Administrators should verify that all instances of S/4HANA Private Cloud are updated to versions where the affected regex patterns have been optimized or replaced with more efficient alternatives. In addition to patching, implementing network-level controls such as Web Application Firewalls can help mitigate the risk by detecting and blocking requests containing suspiciously long strings or known malicious payloads before they reach the application layer. Rate limiting and input validation mechanisms should also be enforced to restrict the size of incoming data fields processed by the vulnerable functionality. Continuous monitoring for unusual spikes in CPU usage associated with web service endpoints can aid in early detection of exploitation attempts, allowing security teams to respond rapidly to potential incidents.