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[crash/fuzzing] DoS/infinite processing during block ssz parsing #1674

pventuzelo opened this issue Apr 27, 2020 · 0 comments · Fixed by #1691

[crash/fuzzing] DoS/infinite processing during block ssz parsing #1674

pventuzelo opened this issue Apr 27, 2020 · 0 comments · Fixed by #1691


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pventuzelo commented Apr 27, 2020


During fuzzing with new version (under development) of beacon-fuzz, I found a bug leading to a Denial of Service (DoS) of teku.
More specifically, an "infinite processing" triggered using teku transition blocks.

Based on other eth2 clients errors, bug seems to be an out-of-bound issue not detected during Teku Block SSZ parsing:

  • lighthouse: Ssz decode failed: OutOfBoundsByte { i: 0 }
  • nim: SszSizeMismatchError

Steps to Reproduce (Bug)

# install
./gradlew distTar installDist

# go to build folder
cd build/install/

# Run teku
bin/teku transition blocks --pre=infinite_process_ssz_state_teku.ssz --network=mainnet infinite_process_ssz_block_teku.ssz


  • Github branch: master
  • Github commit: 1cc3466
  • Java version: openjdk version "11.0.7" 2020-04-14
  • OS Name & Version: Ubuntu 18.04.4 LTS
  • Kernel Version: 4.15.0-96-generic
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