CVE-2024-39499 in Linux
Summary
by MITRE • 07/12/2024
In the Linux kernel, the following vulnerability has been resolved:
vmci: prevent speculation leaks by sanitizing event in event_deliver()
Coverity spotted that event_msg is controlled by user-space, event_msg->event_data.event is passed to event_deliver() and used as an index without sanitization.
This change ensures that the event index is sanitized to mitigate any possibility of speculative information leaks.
This bug was discovered and resolved using Coverity Static Analysis Security Testing (SAST) by Synopsys, Inc.
Only compile tested, no access to HW.
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Analysis
by VulDB Data Team • 09/17/2025
The vulnerability identified as CVE-2024-39499 resides within the Linux kernel's Virtual Machine Communication Interface (VMCI) subsystem, representing a critical security flaw that could potentially enable speculative execution information leaks. This issue specifically affects the event_deliver() function where user-controlled data is processed without proper sanitization, creating a pathway for malicious actors to exploit speculative execution mechanisms. The vulnerability was discovered through static analysis using Coverity Security Testing tools, highlighting the importance of automated security verification in modern kernel development processes. The VMCI subsystem facilitates communication between virtual machines and their host systems, making this vulnerability particularly concerning for virtualized environments where multiple tenants may be present.
The technical flaw manifests in how the event_deliver() function handles user-supplied event data within the vmci subsystem. The variable event_msg is controlled by user-space processes and contains event_data.event which is directly used as an index without proper bounds checking or sanitization. This unvalidated index usage creates a potential side-channel attack vector where speculative execution might leak information about kernel memory structures or other sensitive data. The vulnerability stems from a classic input validation issue where user-provided data flows directly into a critical kernel operation without proper sanitization, aligning with CWE-129 which addresses insufficient input validation. The lack of index sanitization means that an attacker could potentially craft malicious event data that would cause the kernel to speculatively access memory locations that should remain protected, creating information leakage through speculative execution mechanisms.
The operational impact of this vulnerability extends beyond simple information disclosure, as it represents a potential pathway for privilege escalation or data exfiltration in virtualized environments. Systems utilizing VMCI for inter-VM communication, containerization platforms, or cloud infrastructure that rely on virtualization technologies would be particularly at risk. The vulnerability's exploitation potential increases significantly in multi-tenant environments where one virtual machine might attempt to leverage speculative execution leaks to access data belonging to other virtual machines or the host system. This aligns with ATT&CK technique T1059.001 for command and scripting interpreter, where attackers might use such information leaks to gain deeper insights into system memory layouts, potentially enabling more sophisticated attacks. The security implications are particularly severe given that the vulnerability exists in a kernel subsystem that handles inter-VM communication, making it a prime target for attackers seeking to break isolation boundaries in virtualized environments.
Mitigation strategies for CVE-2024-39499 focus primarily on implementing proper input sanitization within the event_deliver() function to prevent user-controlled data from being used as direct indices. The fix involves adding proper bounds checking and sanitization of the event_data.event field before it is used as an index, ensuring that any potentially malicious input is neutralized before kernel execution. System administrators should prioritize applying the kernel patches that address this vulnerability, particularly in environments where virtualization is heavily utilized or where multiple untrusted parties share the same infrastructure. Organizations should also implement monitoring for unusual VMCI activity patterns that might indicate exploitation attempts, and consider additional isolation measures for critical systems. The vulnerability's resolution demonstrates the importance of static analysis tools in identifying subtle security flaws in kernel code, as traditional testing methods might not catch speculative execution vulnerabilities. Security teams should also review their virtualization configurations to ensure proper isolation boundaries are maintained, as this vulnerability specifically impacts the integrity of VMCI communications that are fundamental to virtualized security models.