lwIP SNMP Agent Out-of-Bounds Read Vulnerability

Executive Summary

This vulnerability is an out-of-bounds read flaw in the lwIP library's SNMP agent, specifically in the snmp_pbuf_stream_writeto() function. It occurs because the function incorrectly uses pbuf->len instead of remaining bytes to determine copy bounds. Remote unauthenticated attackers with knowledge of the read community string can send fragmented SNMP requests to receive adjacent receive-buffer or pool memory echoed in responses.

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Detection Guidance

Detect this vulnerability by checking if your system runs lwIP versions 2.0.0 through 2.2.1 with the SNMP agent enabled. Monitor network traffic for fragmented SNMP requests from unauthenticated sources. Use packet capture tools like tcpdump or Wireshark to inspect SNMP traffic for unusual responses containing adjacent memory data.

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Impact Analysis

An attacker could exploit this to read sensitive memory adjacent to the intended SNMP response buffer. This may expose confidential data, system memory contents, or other sensitive information processed by the device running the vulnerable lwIP version. The impact depends on the device's configuration and network exposure.

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Compliance Impact

This vulnerability could lead to unauthorized data exposure, potentially violating GDPR's data protection principles or HIPAA's confidentiality requirements if sensitive personal or health information is leaked. Compliance may be impacted if the affected system processes regulated data.

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Mitigation Strategies

Immediately update lwIP to a patched version beyond 2.2.1. Disable the SNMP agent if not required. Restrict SNMP access via firewalls to trusted sources only. Monitor network traffic for signs of exploitation attempts or unusual SNMP responses.

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