CVE-2016-6560 in osnet-incorporation
Summary
by MITRE
illumos osnet-incorporation bcopy() and bzero() implementations make signed instead of unsigned comparisons allowing a system crash.
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Analysis
by VulDB Data Team • 11/24/2022
The vulnerability identified as CVE-2016-6560 affects the illumos operating system family, specifically within the osnet-incorporation component that provides network stack functionality. This issue resides in the implementation of two fundamental memory manipulation functions bcopy() and bzero() which are critical primitives used throughout the operating system for copying and zeroing memory regions. The flaw manifests in how these functions handle boundary condition checks during memory operations, creating a potential for system instability and denial of service conditions.
The technical root cause of this vulnerability stems from the use of signed integer comparisons instead of unsigned comparisons when validating memory bounds during bcopy() and bzero() operations. When processing memory operations, these functions perform validation checks to ensure that the source and destination memory regions do not exceed allocated boundaries. However, due to the implementation using signed comparisons, certain input values that should be treated as valid unsigned quantities can trigger unexpected behavior in the comparison logic. This occurs because signed comparisons interpret the most significant bit as a sign indicator, causing values that should be considered within bounds to be evaluated as negative numbers, thereby bypassing proper validation checks and potentially leading to memory corruption scenarios.
The operational impact of this vulnerability extends beyond simple system crashes, as it represents a potential pathway for denial of service attacks against systems running affected illumos variants. When the bcopy() or bzero() functions encounter memory operations with specific boundary conditions that trigger the signed comparison flaw, the system may experience unexpected termination, kernel panics, or complete system instability. This vulnerability affects systems that rely heavily on network operations and memory management functions, particularly those implementing network drivers, protocol stacks, and kernel-level network services. The impact is particularly concerning in server environments where sustained availability is critical, as an attacker could potentially exploit this weakness to repeatedly crash system services or entire operating systems.
Systems implementing the affected illumos osnet-incorporation components are vulnerable to exploitation through crafted memory operations that specifically trigger the signed comparison logic error in bcopy() and bzero() implementations. The vulnerability aligns with CWE-191, which describes integer underflow conditions, and more specifically with CWE-190, which addresses integer overflow conditions, as the improper handling of signed versus unsigned comparisons can lead to boundary violations. From an attack perspective, this vulnerability maps to ATT&CK technique T1499.004, which involves network disruption through resource exhaustion or system instability, and T1070.006, which covers data manipulation through system-level memory corruption. The attack surface includes any application or kernel module that utilizes these memory manipulation functions, particularly network stack components, device drivers, and system utilities that perform bulk memory operations.
Mitigation strategies for this vulnerability require immediate patching of the osnet-incorporation component to correct the signed comparison logic in bcopy() and bzero() implementations. System administrators should prioritize applying vendor-provided security updates that modify the comparison operations to use unsigned integers instead of signed integers for boundary validation. Additionally, monitoring should be implemented to detect unusual patterns in memory operations that might indicate exploitation attempts, particularly around network stack functions. The fix should ensure that all boundary condition checks in memory manipulation functions properly handle unsigned integer comparisons to prevent the overflow conditions that lead to system instability. Organizations should also consider implementing additional defensive measures such as kernel memory protection mechanisms and runtime monitoring of critical system functions to detect potential exploitation attempts before they result in system crashes or service disruptions.