CVE-2017-15037 in FreeBSD
Summary
by MITRE
In FreeBSD through 11.1, the smb_strdupin function in sys/netsmb/smb_subr.c has a race condition with a resultant out-of-bounds read, because it can cause t2p->t_name strings to lack a final '\0' character.
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Analysis
by VulDB Data Team • 01/15/2021
The vulnerability identified as CVE-2017-15037 represents a critical race condition flaw within the FreeBSD operating system's SMB implementation that can lead to out-of-bounds memory reads. This issue specifically affects FreeBSD versions through 11.1 and resides in the smb_strdupin function located within the sys/netsmb/smb_subr.c source file. The race condition occurs during the processing of SMB (Server Message Block) network protocol operations, particularly when handling string data transfers between client and server components. The flaw manifests when the t2p->t_name strings fail to properly terminate with a null character, creating a condition where subsequent memory access operations may read beyond allocated buffer boundaries.
The technical nature of this vulnerability stems from improper synchronization mechanisms within the SMB subsystem's string handling routines. When multiple threads or processes access the same memory locations simultaneously, the smb_strdupin function fails to maintain consistent state during string copy operations. This race condition allows for the creation of unterminated strings within the t2p structure's t_name field, which subsequently leads to memory corruption when other parts of the system attempt to process these strings. The absence of proper null termination creates a scenario where memory access operations may traverse into adjacent memory regions, potentially exposing sensitive data or causing system instability.
The operational impact of this vulnerability extends beyond simple memory corruption, as it can be exploited to achieve arbitrary code execution or system denial of service. Attackers who can control network traffic to a FreeBSD system running SMB services may leverage this race condition to manipulate memory contents, potentially leading to privilege escalation or complete system compromise. The out-of-bounds read behavior can expose kernel memory contents to user-space processes, creating potential information disclosure vulnerabilities that align with CWE-129, which addresses improper handling of length parameters. Additionally, this vulnerability fits within the broader category of race condition attacks that are systematically addressed by the ATT&CK framework under the technique of "Race Conditions" (T1494), where adversaries exploit timing vulnerabilities to gain unauthorized access or execute malicious code.
Mitigation strategies for CVE-2017-15037 should focus on implementing proper synchronization mechanisms within the smb_strdupin function to ensure thread-safe string operations. System administrators should apply the official FreeBSD security patches that address this specific race condition by adding appropriate locking mechanisms around the string copy operations. The fix typically involves ensuring that all string operations maintain proper null termination and that concurrent access to shared memory structures is properly synchronized using mutex locks or similar primitives. Organizations should also consider implementing network segmentation and access controls to limit exposure to SMB services, particularly when running older FreeBSD versions that may not have received the specific patch for this vulnerability. Regular security audits and system updates remain crucial for maintaining protection against similar race condition vulnerabilities that could potentially exist in other network protocol implementations.