fuzz: crash in psbt fuzzer #34000

1. 
   fanquake commented at 1:27 pm on December 3, 2025: member

   From: #29675 (review):

   looks like this line crashes:

    0$ echo 'cHNidP8BAP0+AQIAAAAGy4dxGNHKAQgFPtEAoVgyMqb+N0ghgmdne5OjULYs2sUAAAr/AP3////L
    1fnEY0crZmwU+EVahszExpv43SCGCZ2d7k6NQtizaOwADAC4ABHwdAMt+cRjRytmbBT4RVqFYMTGm
    2/jdIIYJnZ3uTo1AAOwAsAAC2KwD9////hqbXlTl39C5ZmAtOAI4+zy32vWLVnyQjw7IvQsBa6rYA
    3AAcAAP3//zKG/zqgb7JIwmli68xeUjUXVp+c4b/tvc55IsAI4yQAAAAAAAAA/f///8t/0cpxGNmb
    4BT4RVqFYMTOm/jdIIXj///8AAAAAgNo7AACAAAD9//3/AiHf9QUAAAAAFgAU9/Ykq9yiCFGnUpsi
    5RsS6FFGLkQEAAAAAAAABABYAFEEQliEApQAADCBABv78gsn+/////wAAAAAAAAAAACIagHQAAAAV
    6DLQyJycoAHNiKDIDAEIAAEEA/wEABgDI/jdIIYJnZ3uTo1AAOwAsAAC2KwD9////hqbXAY9zeZ10
    7c/zcAAEBK2ECEWUrKwAAIlEgcPx0K2ICYgQkKwABAQEBAQsCAgAERUIADwADAAADmSsAAAA=' | base64 --decode > /tmp/crash.bin 
    8
    9
   10$ FUZZ=psbt ./bld-cmake/bin/fuzz -runs=1 /tmp/crash.bin 
   11INFO: Running with entropic power schedule (0xFF, 100).
   12INFO: Seed: 494792800
   13INFO: Loaded 1 modules   (385403 inline 8-bit counters): 385403 [0x55c06b279420, 0x55c06b2d759b), 
   14INFO: Loaded 1 PC tables (385403 PCs): 385403 [0x55c06b2d75a0,0x55c06b8b8d50), 
   15./bld-cmake/bin/fuzz: Running 1 inputs 1 time(s) each.
   16Running: /tmp/crash.bin
   17/usr/bin/../include/c++/v1/span:512: assertion __offset <= size() failed: span<T>::subspan(offset, count): offset out of range
   

   (needs a hardened libc++, msan, or valgrind)

2. fanquake closed this on Dec 3, 2025

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