CVE-2015-9542 in pam_radius
Summary
by MITRE
add_password in pam_radius_auth.c in pam_radius 1.4.0 does not correctly check the length of the input password, and is vulnerable to a stack-based buffer overflow during memcpy(). An attacker could send a crafted password to an application (loading the pam_radius library) and crash it. Arbitrary code execution might be possible, depending on the application, C library, compiler, and other factors.
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Analysis
by VulDB Data Team • 05/15/2023
The vulnerability identified as CVE-2015-9542 affects the pam_radius_auth authentication module version 1.4.0, specifically within the add_password function located in pam_radius_auth.c. This flaw represents a classic stack-based buffer overflow condition that arises from inadequate input validation during password processing. The vulnerability stems from the function's failure to properly verify the length of incoming password data before performing memory copying operations, creating an exploitable condition that can be leveraged by malicious actors to disrupt system operations.
The technical implementation of this vulnerability occurs when the add_password function processes user input without enforcing proper bounds checking on the password length. During the memcpy() operation, the function attempts to copy a password string into a fixed-size buffer without validating whether the source data exceeds the allocated buffer space. This oversight creates a scenario where an attacker can craft a password exceeding the buffer capacity, causing memory corruption that can overwrite adjacent stack memory locations. The vulnerability directly maps to CWE-121 Stack-based Buffer Overflow, which is classified as a critical weakness in software security design.
The operational impact of this vulnerability extends beyond simple service disruption to potentially enable arbitrary code execution within the context of the compromised application. When an application utilizing the pam_radius library processes an attacker-controlled password exceeding the buffer limits, the resulting buffer overflow can cause the application to crash or, in more sophisticated attack scenarios, allow an attacker to inject and execute malicious code. The exploitability of this condition depends on several environmental factors including the specific application loading the library, the underlying C library implementation, compiler optimizations, and memory layout characteristics. This makes the vulnerability particularly dangerous in environments where applications have elevated privileges or where the target system is running with memory protection mechanisms that could be bypassed through successful exploitation.
Mitigation strategies for CVE-2015-9542 should focus on immediate patching of the pam_radius_auth library to version 1.4.1 or later, which contains the necessary bounds checking fixes. Organizations should also implement input validation measures at the application level to prevent overly long password strings from reaching the vulnerable function. Additional defensive measures include enabling compiler-based stack protection mechanisms such as stack canaries, using address space layout randomization to complicate exploitation attempts, and implementing proper memory management practices that enforce strict buffer size validation. From an operational security perspective, monitoring for unusual authentication patterns and implementing intrusion detection systems can help identify potential exploitation attempts targeting this vulnerability, while adherence to the principle of least privilege ensures that even successful exploitation would limit the potential damage to the compromised system.