go-f3 is a Golang implementation of Fast Finality for Filecoin (F3). In versions 0.8.6 and below, go-f3 panics when it validates a "poison" messages causing Filecoin nodes consuming F3 messages to become vulnerable. A "poison" message can can cause integer overflow in the signer index validation, which can cause the whole node to crash. These malicious messages aren't self-propagating since the bug is in the validator. An attacker needs to directly send the message to all targets. This issue is fixed in version 0.8.7.

Affected: Go: github.com/filecoin-project/go-f3

### Impact

Filecoin nodes consuming F3 messages are vulnerable. go-f3 panics when it validates a "poison" messages. A "poison" message can can cause integer overflow in the signer index validation. In Lotus' case, the whole node will crash.

There is no barrier to entry. An attacker doesn't need any power to pull off this attack.

These malicious messages aren't self-propagating since the bug is in the validator. An attacker needs to directly send the message to all targets.

### Patches The fix was merged and released with go-f3 0.8.7. All node software (Lotus, Forest, Venus) are using a patched version of go-f3 with their updates for the nv27 network upgrade.

go-f3 now does proper overflow checking using `math.MaxInt64` comparison and returns error `"justificationPower overflow"` when overflow would occur.

### Workarounds The are no immediate workarounds available. Nodes should upgrade to the patched version, which they will have done if participating in nv27 on Filecoin mainnet.

### Credits The initial finding(unrelated path) was reported by [0xNirix](https://github.com/0xNirix) via bug bounty program which wasn't high issue. The further digging by developers led to this finding. Thank you for the contributions.

govulncheck-vulndb-0.0.20251023T162509-1.1 on GA media