CVE-2017-8039 in Spring Web Flow
Summary
by MITRE
An issue was discovered in Pivotal Spring Web Flow through 2.4.5. Applications that do not change the value of the MvcViewFactoryCreator useSpringBinding property which is disabled by default (i.e., set to 'false') can be vulnerable to malicious EL expressions in view states that process form submissions but do not have a sub-element to declare explicit data binding property mappings. NOTE: this issue exists because of an incomplete fix for CVE-2017-4971.
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Analysis
by VulDB Data Team • 01/25/2021
The vulnerability identified as CVE-2017-8039 represents a critical server-side template injection flaw within Pivotal Spring Web Flow framework versions up to 2.4.5. This security weakness specifically affects applications that rely on the default configuration of MvcViewFactoryCreator with the useSpringBinding property set to false, creating an exploitable condition that allows attackers to inject malicious expression language expressions into view states. The vulnerability stems from an incomplete remediation of a previous issue CVE-2017-4971, indicating that the security team's initial fix was insufficient to address all attack vectors within the framework's view processing mechanisms.
The technical flaw manifests when applications process form submissions through view states that lack explicit data binding property mappings, creating a pathway for malicious users to execute arbitrary expression language code within the application context. This occurs because the framework fails to properly sanitize or validate user input that flows into view state processing when the useSpringBinding flag remains disabled. The vulnerability operates at the intersection of expression language processing and view state management, where user-supplied data can be interpreted as executable code rather than simple input, leading to potential code execution and system compromise.
Operationally, this vulnerability poses significant risks to applications utilizing Spring Web Flow, particularly those that accept user input through forms and process it within view states without explicit binding declarations. Attackers can leverage this weakness to execute arbitrary commands on the server, potentially leading to complete system compromise, data exfiltration, or denial of service conditions. The impact is amplified in environments where applications process untrusted user input without proper validation or sanitization, as the vulnerability effectively bypasses normal input processing controls and allows direct execution of expression language constructs within the application's runtime environment.
Organizations should immediately upgrade to patched versions of Spring Web Flow beyond 2.4.5 to address this vulnerability, while also implementing immediate mitigations such as enabling the useSpringBinding property explicitly, validating all user input through comprehensive sanitization processes, and implementing strict input validation controls for form submissions. Additionally, security teams should conduct thorough code reviews to identify applications that may be using the vulnerable default configurations, and implement monitoring solutions to detect potential exploitation attempts. This vulnerability aligns with CWE-94, which describes improper control of generation of code, and maps to ATT&CK technique T1059.007 for execution through expression language, emphasizing the need for robust input validation and secure coding practices throughout the application development lifecycle.