CVE-2020-8927: Buffer Overflow in Brotli Library in Bitnami .NET

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Background

Bitnami .NET is a package that provides a development environment for building applications using the .NET framework. It includes various tools and libraries to facilitate the development process. One of the libraries included is the Brotli library, which is used for compression and decompression of data. The Brotli library versions prior to 1.0.8 are vulnerable to a buffer overflow issue.

Vulnerability Detail

The vulnerability (CVE-2020-8927) in the Brotli library allows an attacker to trigger a crash by controlling the input length of a "one-shot" decompression request to a script. This crash occurs when copying over chunks of data larger than 2 GiB. The impact of this vulnerability can lead to denial of service (DoS) attacks or potential remote code execution. It is recommended to update the Brotli library to version 1.0.8 or later. Alternatively, using the "streaming" API instead of the "one-shot" API and imposing chunk size limits can mitigate the risk.

Workaround

If updating the Brotli library is not feasible, a workaround is to switch to using the "streaming" API instead of the "one-shot" API. This can be done by modifying the code to use the appropriate API calls. Additionally, developers should impose chunk size limits to prevent the buffer overflow. Here is an example of how to use the streaming API in C#:

// Create a Brotli decompressor
var decompressor = new BrotliDecompressor();

// Create a buffer to hold the decompressed data
var buffer = new byte[4096];

// Read the compressed data from the input stream
var compressedData = ReadCompressedData();

// Create a MemoryStream to hold the decompressed data
using (var decompressedStream = new MemoryStream())
{
    // Create a BrotliStream with the decompressed stream and the decompressor
    using (var brotliStream = new BrotliStream(decompressedStream, CompressionMode.Decompress, true))
    {
        // Read the compressed data into the buffer and write it to the BrotliStream
        brotliStream.Write(compressedData, 0, compressedData.Length);
    }

    // Get the decompressed data from the MemoryStream
    var decompressedData = decompressedStream.ToArray();
}

Conclusion

The buffer overflow vulnerability in the Brotli library (CVE-2020-8927) poses a risk to applications using the Bitnami .NET package. It is crucial to update the Brotli library to version 1.0.8 or later to mitigate the vulnerability. Alternatively, switching to the "streaming" API and imposing chunk size limits can also help prevent the buffer overflow. For further assistance and support in addressing this vulnerability, please contact DevNack.com.

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