Executive Summary

CVE-2016-20043 is a stack buffer overflow vulnerability in NRSS RSS Reader version 0.3.9-1. It occurs when a local attacker supplies an oversized argument to the program's -F parameter. Specifically, by providing input with 256 bytes of padding followed by a controlled value, the attacker can overwrite the return address on the stack (Extended Instruction Pointer, EIP). This allows the attacker to redirect the program's execution flow and execute arbitrary code with the privileges of the NRSS Reader process.

The vulnerability is a classic stack-based buffer overflow where the attacker crafts a malicious input to overflow the buffer and overwrite the return address, enabling code execution. Exploits use a NOP sled and shellcode to execute commands such as spawning a shell.

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Impact Analysis

This vulnerability allows a local attacker to execute arbitrary code on the affected system with the same privileges as the NRSS RSS Reader process. This can lead to unauthorized actions such as gaining shell access, executing malicious commands, or compromising the system integrity.

Because the exploit requires local access but no special privileges or user interaction, any user with access to the system could potentially exploit this vulnerability to escalate their capabilities or cause damage.

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Detection Guidance

This vulnerability can be detected by testing the NRSS RSS Reader 0.3.9-1 application locally with a crafted input to the -F parameter that causes a stack buffer overflow.

A practical detection method is to run the vulnerable program with an argument consisting of 256 'A' characters followed by 'DCBA' to the -F option and observe if a segmentation fault occurs with the instruction pointer (EIP) overwritten by 0x41424344 (ASCII for 'DCBA').

For example, you can execute a command similar to the following in a Linux environment where the NRSS Reader binary is accessible:

• ./nrss -F $(python -c 'print("A"*256 + "DCBA")')

If the program crashes with a segmentation fault and the EIP register is overwritten with 0x41424344, it confirms the presence of the vulnerability.

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Mitigation Strategies

Immediate mitigation steps include restricting local access to the NRSS RSS Reader 0.3.9-1 application to trusted users only, as the vulnerability requires local access to exploit.

Avoid running the vulnerable version of the NRSS Reader or executing it with untrusted input, especially avoiding the use of the -F parameter with user-supplied arguments.

If possible, update or patch the NRSS RSS Reader to a version that addresses this stack buffer overflow vulnerability.

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Compliance Impact

The vulnerability allows local attackers to execute arbitrary code with the privileges of the NRSS RSS Reader process by exploiting a stack buffer overflow. This can lead to unauthorized access or control over the affected system.

Such unauthorized code execution and potential system compromise can impact compliance with common standards and regulations like GDPR and HIPAA, which require protection of sensitive data and system integrity.

Specifically, if the NRSS RSS Reader is used in environments handling personal or protected health information, exploitation of this vulnerability could lead to data breaches or unauthorized data access, violating confidentiality and integrity requirements mandated by these regulations.

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