CVE-2010-2530 in NetBSD
Summary
by MITRE
Multiple integer signedness errors in smb_subr.c in the netsmb module in the kernel in NetBSD 5.0.2 and earlier, FreeBSD, and Apple Mac OS X allow local users to cause a denial of service (panic) via a negative size value in a /dev/nsmb ioctl operation, as demonstrated by a (1) SMBIOC_LOOKUP or (2) SMBIOC_OPENSESSION ioctl call.
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Analysis
by VulDB Data Team • 04/28/2017
The vulnerability described in CVE-2010-2530 represents a critical integer signedness error within the kernel-level networking subsystem of several operating systems including NetBSD 5.0.2 and earlier versions, FreeBSD, and Apple Mac OS X. This flaw exists in the netsmb module's smb_subr.c file, which handles server message block protocol operations. The issue manifests when local attackers manipulate ioctl operations targeting the /dev/nsmb device interface, specifically through SMBIOC_LOOKUP or SMBIOC_OPENSESSION commands. The root cause stems from improper handling of signed integer values during size parameter validation, creating a scenario where negative values can bypass normal bounds checking mechanisms.
The technical exploitation of this vulnerability occurs through careful manipulation of ioctl parameters that control network session management operations. When a negative size value is passed to the smb_subr.c functions, the kernel's integer handling logic fails to properly validate the input, leading to undefined behavior in memory allocation or buffer management routines. This flaw falls under CWE-191, which specifically addresses integer underflow conditions, and can be categorized as a kernel-level denial of service vulnerability. The attack vector requires local system access, making it a privilege escalation concern that could potentially be leveraged in more complex attack chains. The vulnerability demonstrates poor input validation practices where signed integer comparisons fail to account for negative values that should be rejected as invalid parameters.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as kernel panics can result in complete system instability and require manual rebooting of affected systems. The nature of the flaw means that any local user with access to the /dev/nsmb device interface can trigger this condition, making it particularly concerning for multi-user environments or systems where untrusted users might have access to local resources. The vulnerability affects core networking functionality and could potentially disrupt network services that depend on SMB protocol operations. From an attacker's perspective, this represents a low-effort, high-impact method to cause system downtime, with the added risk that kernel panics could potentially be exploited to gain further privileges or access to sensitive system resources.
Mitigation strategies for this vulnerability require immediate patching of affected operating systems, as the fix involves correcting the integer validation logic in the smb_subr.c file to properly reject negative size parameters. System administrators should prioritize updating their NetBSD, FreeBSD, and Mac OS X installations to versions that contain the patched kernel modules. Additionally, access controls should be implemented to restrict local access to the /dev/nsmb device interface where possible, and monitoring should be enabled to detect unusual ioctl operations targeting these interfaces. The vulnerability highlights the importance of proper input validation in kernel space code and demonstrates the critical need for thorough testing of integer handling logic, particularly in security-sensitive subsystems. Organizations should also consider implementing intrusion detection systems that can identify suspicious ioctl patterns and maintain comprehensive system logging for forensic analysis in case of exploitation attempts.