Integer Calculation Error in BusyBox wget Leading to Heap Buffer Overflow

Executive Summary

This vulnerability is a heap-based buffer overflow in BusyBox's wget utility when resuming FTP downloads. It occurs because wget does not verify if the resume offset exceeds the file size reported by the server, leading to an integer calculation error. A malicious FTP server or network attacker can exploit this by providing crafted file size metadata, causing a buffer overflow with attacker-controlled data.

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Detection Guidance

Detecting this vulnerability requires checking if BusyBox's wget utility is installed and vulnerable. Inspect the version of BusyBox using commands like 'busybox | head -n 1' or 'busybox wget --version'. If the version is affected, monitor network traffic for FTP download resumption attempts with suspicious file size metadata. Security scanners may flag this issue, but false positives are possible due to versioning differences.

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Impact Analysis

Exploitation may allow an attacker to execute arbitrary code or crash the application, resulting in a denial of service. This requires the user to interact with a compromised FTP host or an unencrypted network attacker during a file resumption transfer.

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Mitigation Strategies

Immediately stop using BusyBox's wget for FTP downloads, especially resumption. Upgrade to a patched version of BusyBox if available. If upgrading is not possible, avoid using wget for FTP entirely or switch to a secure alternative like SFTP/SCP. Monitor for exploitation attempts in network logs.

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