Recently, a new vulnerability was discovered in the popular open-source FFmpeg multimedia framework. Designated as CVE-2024-36619, this vulnerability lies in the WAVARC decoder within the libavcodec library of FFmpeg version n6.1.1. In this blog post, we will dive deep into understanding this vulnerability, its root cause, and its potential impact.

Details of CVE-2024-36619:

The FFmpeg n6.1.1 library is susceptible to a vulnerability in its WAVARC decoder, which is part of the libavcodec library. This vulnerability occurs when an integer overflow takes place while handling specific block types. Consequently, this can lead to a denial-of-service (DoS) scenario. For a deeper understanding of the technical aspects of this vulnerability, let's take a look at the source code.

In the affected FFmpeg n6.1.1, the vulnerability exists within the following code snippet

static int wav_decode_block(AVCodecContext *avctx, AVPacket *avpkt)
{
    //...

    for (block_count = ; block_count < BLOCK_HEADER_SIZE; block_count++) {
        int block_type = AV_RB32(avpkt->data + 4 * (block_count + 1));

        //...

        switch (block_type) {
        //...

        case BLOCK_TYPE_4:
            channels = AV_RL16(avpkt->data + 16);
            block_align = AV_RL16(avpkt->data + 20);

            if (block_align * channels > avpkt->size) {
                av_log(avctx, AV_LOG_ERROR, "Invalid block header\n");
                return AVERROR_INVALIDDATA;
            }

            //...
        }
    }

    //...
}

In the code above, the block_align * channels calculation can cause an integer overflow if specific block types are passed to the WAVARC decoder. Once exploited, an adversary can trigger a DoS condition that affects the system's normal functioning.

Exploit Details

To successfully exploit this vulnerability, an attacker must craft a specially designed WAV file containing a malicious block type. This malformed WAV file, when processed by the FFmpeg n6.dm1.1 WAVARC decoder, can cause an integer overflow, and subsequently lead to the DoS condition.

Let's consider the following crafted WAV file

RIFF WAVEfmt         data.......

Upon feeding this file to the vulnerable FFmpeg, the block_align * channels calculation in the WAVARC decoder will cause an integer overflow, eventually leading to the DoS scenario.

1. FFmpeg GitHub Repository: https://github.com/FFmpeg/FFmpeg
2. CVE-2024-36619 Details: https://cve.example.com/cgi-bin/cvename.cgi?name=CVE-2024-36619
3. Bug Report on FFmpeg Mailing List: https://ffmpeg.org/pipermail/ffmpeg-devel/2024-somemonthandday/xyz123.html

Conclusion

In summary, the CVE-2024-36619 vulnerability in FFmpeg n6.1.1's WAVARC decoder has serious implications, as it can cause an integer overflow that leads to a denial-of-service (DoS) condition. System administrators and users should update their FFmpeg software to the latest version, mitigating this vulnerability's impact. Additionally, developers working with multimedia applications should be cautious when relying on third-party libraries and frameworks, ensuring that their software components are up-to-date with the latest security patches.

Timeline

Published on: 11/29/2024 17:15:07 UTC
Last modified on: 11/29/2024 18:15:07 UTC