CVE-2017-7696 in AS JAVA SSO Authentication Library
Summary
by MITRE
SAP AS JAVA SSO Authentication Library 2.0 through 3.0 allow remote attackers to cause a denial of service (memory consumption) via large values in the width and height parameters to otp_logon_ui_resources/qr, aka SAP Security Note 2389042.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 08/31/2020
The vulnerability identified as CVE-2017-7696 affects SAP Application Server Java SSO Authentication Library versions 2.0 through 3.0, representing a critical denial of service weakness that can be exploited remotely by attackers to consume excessive system memory. This vulnerability specifically targets the otp_logon_ui_resources/qr endpoint within the authentication framework, where malicious actors can manipulate the width and height parameters to trigger memory exhaustion conditions. The flaw resides in how the system processes image generation requests for QR codes used in one-time password authentication, creating a scenario where malformed parameters can lead to unbounded memory allocation.
The technical implementation of this vulnerability stems from inadequate input validation and parameter handling within the QR code generation module. When attackers submit unusually large values for the width and height parameters, the system attempts to allocate memory proportional to these values without proper bounds checking or resource limits. This behavior aligns with CWE-131, which describes improper handling of length parameters in memory allocation functions, and can be categorized under CWE-400 as an unchecked resource allocation vulnerability. The system's failure to implement reasonable upper limits on image dimensions allows for exponential memory consumption that can quickly overwhelm available system resources.
From an operational perspective, this vulnerability presents significant risks to SAP environments as it enables attackers to disrupt authentication services through simple HTTP requests. The impact extends beyond immediate service disruption to potentially affecting other system components that depend on the authentication infrastructure. Attackers can exploit this weakness without requiring authentication credentials, making it particularly dangerous as it can be used for both denial of service attacks and as a precursor to more sophisticated exploitation attempts. The vulnerability's presence in the SSO authentication library means that successful exploitation could compromise the entire authentication ecosystem within affected SAP systems, potentially affecting multiple applications that rely on the same authentication framework.
The attack vector for CVE-2017-7696 follows the patterns described in the MITRE ATT&CK framework under technique T1499, specifically focusing on network denial of service attacks. The exploitation requires only basic web request capabilities and does not necessitate advanced technical skills or privileged access, making it accessible to a broad range of threat actors. Organizations should consider implementing network-level mitigations such as rate limiting and parameter validation at the perimeter, though these approaches may not fully address the root cause. The most effective remediation strategy involves applying the official SAP security note 2389042 patches that address the input validation issues and implement proper bounds checking for image dimension parameters. Additionally, system administrators should monitor for unusual memory consumption patterns and implement appropriate resource limits to prevent complete system exhaustion. The vulnerability highlights the importance of proper input validation in web applications and demonstrates how seemingly innocuous functionality can become a security risk when proper resource management practices are not implemented.