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The Most Dangerous Codec in the World: Finding and Exploiting Vulnerabilities in H.264 Decoders
Discover vulnerabilities in widely used H.264 decoders, including Apple's D5500 Kext, and learn how to exploit them through thumbnailing and stateless video decoding.
- H.264 is a widely supported and complex codec with a massive attack surface.
- The codec’s syntax and semantics are not always correctly implemented, leading to vulnerabilities.
- The presentation highlights a series of vulnerabilities discovered in the Apple D5500 Kext using H.264.
- The first vulnerability is a controlled kernel heap write that can be triggered via thumbnailing.
- The second vulnerability is a stateless video decoder initiative by the Video for Linux folks that aims to remove syntax element parsing from the Linux kernel.
- H.264 can be used to generate specially crafted videos to test decoders for vulnerabilities.
- The presentation also highlights the need for better tooling to help researchers discover and investigate vulnerabilities in video decoders.
- The vulnerabilities discovered in this presentation demonstrate the importance of accurate syntax and semantics checking in video decoders.
- The presentation also discusses the challenges of modifying syntax elements manually and the need for better tooling to make this process simpler.
- Possible solutions include using emulation prevention bytes and implementing semantic checks in video decoders.
- The presentation concludes by highlighting the need for more research into video decoders and the importance of better tooling to help researchers discover and investigate vulnerabilities.