cl/sentinel: fix panic on short attnets ENR entry#20492
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AskAlexSharov merged 1 commit intomainfrom Apr 11, 2026
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A malformed attnets ENR can decode into a Bitvector64 shorter than 8 bytes, causing 'index out of range' panic in findPeersForSubnets when indexing peerSubnets[subnetIdx/8]. Reject such nodes.
domiwei
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Apr 11, 2026
AskAlexSharov
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Apr 11, 2026
Cherry-pick of #20492 to release/3.4. ## Summary Fixes a panic seen in the wild: ``` panic: runtime error: index out of range [4] with length 1 cl/sentinel.(*Sentinel).findPeersForSubnets.func1 cl/sentinel/discovery.go:80 ``` A malformed/short `attnets` ENR entry decodes into a `bitfield.Bitvector64` shorter than the expected 8 bytes, so indexing `peerSubnets[subnetIdx/8]` goes out of range when `subnetIdx >= 8`. Adds a `len(peerSubnets) == 8` guard at all three call sites in `cl/sentinel/discovery.go`.
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Summary
Fixes a panic seen in the wild:
A malformed/short
attnetsENR entry decodes into abitfield.Bitvector64shorter than the expected 8 bytes, so indexingpeerSubnets[subnetIdx/8]goes out of range whensubnetIdx >= 8.Adds a
len(peerSubnets) == 8guard at all three call sites incl/sentinel/discovery.go(findPeersForSubnetsfilter, post-connect coverage update, andonConnectionunderserved-subnet check).