CVE-2004-2395 in Linux
Summary
by MITRE
Memory leak in passwd 0.68 allows local users to cause a denial of service (memory consumption) via a large number of failed read attempts from the password buffer.
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Analysis
by VulDB Data Team • 06/29/2018
The vulnerability identified as CVE-2004-2395 represents a classic memory management flaw within the passwd utility version 0.68 that operates at the system level. This issue manifests as a memory leak that occurs during the processing of password buffer operations, specifically when the system encounters a large number of failed read attempts. The flaw resides in the software's inability to properly release allocated memory resources after unsuccessful authentication attempts, creating a gradual accumulation of memory consumption that can eventually lead to system instability.
The technical implementation of this vulnerability demonstrates poor resource management practices where the passwd utility fails to correctly handle error conditions during password input processing. When multiple failed read attempts occur, the system allocates memory to store intermediate buffer states and authentication attempts without subsequently freeing this memory space. This behavior creates a memory leak that grows progressively with each failed authentication attempt, as the utility maintains references to previously allocated memory segments that should be released upon completion of processing. The vulnerability specifically targets the password buffer handling mechanism, where the system's failure to properly manage memory allocation during error conditions results in sustained memory consumption.
From an operational perspective, this vulnerability enables local attackers to execute a denial of service attack against the target system by repeatedly attempting to read from the password buffer with invalid inputs. The cumulative effect of these failed attempts causes progressive memory exhaustion, which can lead to system performance degradation, application crashes, or complete system unresponsiveness. The attack vector is particularly concerning because it requires minimal privileges and can be executed by any local user with access to the system's password handling mechanisms. The impact extends beyond simple resource exhaustion to potentially affect other system services that depend on adequate memory availability, creating cascading failures that can compromise overall system integrity and availability.
The vulnerability aligns with CWE-401, which categorizes memory leaks as a fundamental weakness in memory management practices. This classification reflects the core issue where allocated memory resources are not properly deallocated, creating a persistent drain on system resources. From an attacker's perspective, this vulnerability fits within the ATT&CK technique T1499.004, which describes the use of resource exhaustion attacks to cause denial of service conditions. The attack pattern demonstrates how seemingly benign system operations can be exploited to create persistent resource consumption that degrades system performance over time. Additionally, this vulnerability highlights the importance of proper error handling and resource cleanup in system-level utilities, as the flaw exists in fundamental memory management practices rather than complex cryptographic or network protocols.
Mitigation strategies for this vulnerability should focus on implementing proper memory management practices within the passwd utility and related system components. System administrators should ensure that all versions of the passwd utility are updated to include proper memory deallocation mechanisms that release allocated resources after each authentication attempt, regardless of success or failure. The implementation should include comprehensive error handling that ensures memory cleanup occurs even when unexpected conditions arise during buffer processing. Additionally, system monitoring should be enhanced to detect unusual memory consumption patterns that may indicate exploitation of this vulnerability. Regular patch management procedures should be enforced to ensure that all system components receive timely updates addressing known memory management flaws. The vulnerability also underscores the need for thorough code review processes that examine resource allocation and deallocation patterns, particularly in system utilities that handle sensitive information like passwords.