CVE-2007-3105 in Linux
Summary
by MITRE
Stack-based buffer overflow in the random number generator (RNG) implementation in the Linux kernel before 2.6.22 might allow local root users to cause a denial of service or gain privileges by setting the default wakeup threshold to a value greater than the output pool size, which triggers writing random numbers to the stack by the pool transfer function involving "bound check ordering". NOTE: this issue might only cross privilege boundaries in environments that have granular assignment of privileges for root.
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Analysis
by VulDB Data Team • 07/25/2019
The vulnerability described in CVE-2007-3105 represents a critical stack-based buffer overflow within the Linux kernel's random number generator implementation. This flaw exists in kernel versions prior to 2.6.22 and specifically targets the pool transfer function that handles the generation and distribution of random numbers. The vulnerability stems from improper bound checking mechanisms that fail to validate the relationship between the wakeup threshold and the output pool size, creating a condition where malicious input can trigger unintended memory operations.
The technical exploitation of this vulnerability occurs through a specific sequence involving the manipulation of the default wakeup threshold parameter. When this threshold is set to a value exceeding the output pool size, the pool transfer function attempts to write random numbers to the stack memory region. The flaw lies in the ordering of bound checks within the code implementation, which allows the overflow to occur before proper validation can prevent it. This creates a classic stack buffer overflow scenario where the overflowed data can overwrite adjacent stack memory, potentially including return addresses and other critical control structures.
From an operational impact perspective, this vulnerability presents a significant privilege escalation risk for local attackers who can manipulate the random number generator parameters. The flaw can potentially lead to both denial of service conditions and local root privilege escalation, depending on the specific execution environment and system configuration. The vulnerability's exploitation requires local access and the ability to modify kernel parameters, but once successful, it provides attackers with elevated privileges that can compromise the entire system. The severity is amplified in environments where root privileges are granularly assigned and where attackers might have limited initial access but can leverage this vulnerability to gain full system control.
The vulnerability aligns with CWE-121 Stack-based Buffer Overflow, which specifically addresses buffer overflows occurring in stack memory regions due to inadequate bounds checking. This classification indicates that the flaw represents a fundamental issue in memory management within kernel space operations. The exploitability of this vulnerability also connects to ATT&CK technique T1068, which covers privilege escalation through local exploits that manipulate system resources. The specific nature of this vulnerability makes it particularly dangerous in multi-user environments where local access might be obtained through various means, including social engineering or other initial compromise techniques.
Mitigation strategies for CVE-2007-3105 require immediate kernel version upgrades to 2.6.22 or later, where the bound checking order has been corrected to prevent the overflow condition. System administrators should also implement proper access controls and privilege management to limit local user capabilities, as the vulnerability requires local access to manipulate the affected parameters. Additionally, monitoring for unusual parameter changes in kernel random number generator settings can help detect potential exploitation attempts. The fix implemented in kernel 2.6.22 addresses the core issue by correcting the bound check ordering, ensuring that the wakeup threshold is properly validated against the pool size before any memory operations occur. Organizations should also consider implementing kernel hardening measures and regular security audits to identify similar vulnerabilities in other system components that might present similar bound checking flaws.