Citizenlab discovered BLASTPASS, a 0day being actively exploited in the image format WebP. Known as CVE20234863 and CVE202341064, an issue in webp's build huffman table function can lead to a heap buffer overflow. This vulnerability is very interesting and I'm excited to share with you what I learned.

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WebP Fix Commit: https://chromium.googlesource.com/web...
Citizenlab: https://citizenlab.ca/2023/09/blastpa...
Ben Hawkes: https://blog.isosceles.com/thewebp0...

Software Updates
Apple https://support.apple.com/engb/106361
Chrome https://chromereleases.googleblog.com...
Firefox https://www.mozilla.org/enUS/securit...
Android https://www.mozilla.org/enUS/securit...
Whose CVE is it Anyway? https://adamcaudill.com/2023/09/14/wh...

References:
2014 bug introduction https://github.com/webmproject/libweb...
   • How Computers Compress Text: Huffman ...  
   • Huffman Codes: An Information Theory ...  
   • How PNG Works: Compromising Speed for...  
   • Huffman coding stepbystep example  
https://stackoverflow.com/questions/1...
https://web.archive.org/web/202302042...
enough.c https://github.com/madler/zlib/blob/d...

Thanks to:
  / mistymntncop  
  / benhawkes  


Chapters:
00:00 Intro to CVE20234863
01:32 Most Valuable Vulnerability?
03:02 Heap Overflow Related to Huffman Trees
03:58 Learning about Huffman Codes
06:24 What are Huffman Tables?
10:24 Hardcoded Table Sizes (enough.c)
12:21 Code Walkthrough BuildHuffmanTable()
13:04 The code_lengths[] and count[] Arrays
15:14 Difference Between Compression and Decompression!
17:04 Outro

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