CVE-2003-0961 in Linux
Summary
by MITRE
Integer overflow in the do_brk function for the brk system call in Linux kernel 2.4.22 and earlier allows local users to gain root privileges.
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Analysis
by VulDB Data Team • 07/20/2025
The vulnerability identified as CVE-2003-0961 represents a critical integer overflow flaw within the Linux kernel's memory management subsystem, specifically affecting versions 2.4.22 and earlier. This vulnerability resides in the do_brk function which handles the brk system call, a fundamental mechanism for dynamically adjusting the program break of a process. The integer overflow occurs when the kernel processes memory allocation requests that exceed the maximum allowable value for a signed integer, creating a condition where the system's memory management logic becomes corrupted and potentially exploitable.
The technical implementation of this vulnerability exploits the way the Linux kernel handles memory segment boundaries during process execution. When a process invokes the brk system call to adjust its heap size, the kernel must validate and manage memory allocation boundaries. In vulnerable versions, the do_brk function fails to properly validate the input parameters, particularly when dealing with large memory requests that approach integer limits. This flaw allows a local attacker to manipulate memory allocation parameters such that the integer arithmetic overflows, causing unexpected behavior in memory management structures. The overflow can result in memory regions being incorrectly mapped or accessible, creating opportunities for privilege escalation.
The operational impact of this vulnerability is severe as it enables local users to escalate their privileges from standard user level to root access without requiring authentication or special privileges. An attacker can leverage this vulnerability by crafting specific memory allocation requests that trigger the integer overflow condition, potentially leading to memory corruption that allows arbitrary code execution with elevated privileges. This represents a classic local privilege escalation vector that can be exploited by any user with access to the system, making it particularly dangerous in multi-user environments where users might not be trusted. The vulnerability essentially undermines the kernel's memory protection mechanisms and can lead to complete system compromise.
The underlying cause of this vulnerability aligns with CWE-190, which addresses integer overflow conditions, and demonstrates how improper input validation in kernel space can lead to critical security flaws. From an ATT&CK perspective, this vulnerability maps to privilege escalation techniques under the T1068 category, specifically targeting kernel-level exploits that leverage memory corruption vulnerabilities. The exploitability of this vulnerability is enhanced by the fact that it requires no special privileges to initiate, making it accessible to any local user. Recommended mitigations include upgrading to kernel versions 2.4.23 or later where this vulnerability has been patched, implementing proper integer overflow checks in memory management functions, and applying kernel hardening measures such as stack canaries and address space layout randomization. Organizations should also conduct thorough security assessments of their kernel versions and ensure timely patch management to prevent exploitation of similar vulnerabilities in the memory subsystem.