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Ravencoin (RVN) Consensus Exploit and Chain Recovery
This was the most serious incident on any of our pools this year, so here is the whole thing in order.
What broke
The flaw sits in Ravencoin’s KAWPOW block header validation. The nHeight field inside the KAWPOW header was never checked against the block’s actual position in the chain. An attacker who manipulates that field can get a vulnerable node to accept a supplied mix hash without ever doing the real ProgPoW work – no DAG, no memory-hard hashing, no GPU. Forging a block that way is orders of magnitude cheaper than mining one honestly.
The bug had two ugly side effects beyond the forged blocks themselves. Affected nodes could crash on restart, and nodes trying to sync ran into broken header sequences and stalled.
Timeline
- August 7, 15:44:01 UTC – the first known invalid block is accepted at height 4,487,776. A self-described security researcher demonstrated the attack on mainnet, and a second attacker copied it.
- August 10 – 2Miners releases the emergency patch 4.6.1.1-hf1. It rejects any block whose declared header height does not match its actual position in the chain, and locks a checkpoint at block 4,487,775, the last clean block.
- August 10-12 – Upbit and Bitget suspend RVN deposits and withdrawals as a precaution.
- August 11 – Ravencoin publicly discloses the vulnerability and advises node operators, exchanges, and explorers to upgrade immediately. Maintainer Hans Schmidt recommends running the 2Miners code until a combined upstream release is ready.
- August 19 – Ravencoin publishes v4.8.0, built on the same code we released, bundling the KAWPOW fix with the separate asset transfer quantity overflow patch.
How big the damage was
Scanning a 2,089-block window from 4,489,527 to 4,491,615, we identified 96 forged blocks. Everything confirmed after 4,487,775 on the exploited branch was at risk, which is roughly three days of chain history.
The recovery chain
2Miners and the other pools started building a competing chain from block 4,487,776 that excludes the branch carrying the invalid blocks. Together we hold the majority of Ravencoin’s hash rate, so the clean chain grew faster than the forged one and overtook it. It is now thousands of blocks ahead, peers have reconnected, and the split is settled in favour of the honest chain.
Every RVN mined before August 7 was never in question. Our RVN pool and RVN SOLO have been running on the clean chain throughout.
What you need to do
- Run v4.8.0 if you operate your own node, wallet, explorer, or exchange integration. It supersedes our emergency hotfix 4.6.1.1-hf1.
- v4.7.0 does not fix this. That release only patched the asset overflow bug and never activated on mainnet, because BIP9 voting did not complete before v4.8.0 became necessary.
- Anything older than 4.6.1.1-hf1 is still exposed to the same forged-block trick and may refuse to sync.
If you mine RVN with us and do not run your own node, there is nothing to change on your side. KAWPOW mining and payouts continue as normal.
Pearl (PRL) Salted Noise-Seed Hard Fork at Block 99,000
Pearl activated a hard fork at mainnet block 99,000 on August 11. The change salts the noise seed used by PearlHash, which means shares produced by pre-fork mining software are simply invalid after the fork block.
Please pay attention! This failure mode is quiet. An outdated miner keeps reporting a healthy hashrate on your screen while nothing it submits gets credited. If your PRL earnings flatlined in mid-August, this is why.
Mining software with fork support:
- PeakMiner 2.9.0
- SRBMiner 3.5.3
- Krig 1.2.0
- ArcMiner 0.3.1
- Fl4shMiner 1.2.7
- ForgeMiner 1.5.10
On the node side the fork ships in Pearl 1.4.1, and that is what our node runs. Earlier in the month we also took Pearl 1.3.1 (commit b6d7e5e), a follow-up to the 1.3.0 rank-penalty soft fork released on August 5. Our pools were ready before the fork block and kept producing. Mine on PRL POOL and PRL SOLO, and check profitability on 2CryptoCalc.
Kaspa (KAS) Block Reward Reduction
As defined by the Kaspa Tokenomics, the Crescendo Hard Fork, and the official emission schedule, Kaspa underwent another scheduled block reward reduction in August.
- Previous Reward: 2.449 KAS
- New Reward: 2.312 KAS
Please pay attention! Kaspa mining profitability has changed. We have already updated 2CryptoCalc to reflect the new reward values. Mining continues on the KAS pool and KAS SOLO.
Node Updates
Ergo – 6.0.4
Released August 18. Most of this release is API hardening and test work, but three items matter if you run an Ergo node or care about block propagation:
- Block candidate generation improvements
- A fix for lastHeaders in the upcoming state context, so the miner no longer gets stuck on divergence during block pre-validation and validation
- A caught-up fix, plus extra index consistency preserved across chain switches
The rest is housekeeping: duplicate IDs are now prevented in the ordered transaction pool, several REST and wallet routes validate their parameters properly, and the testnet version 2 activation height was corrected. Autolykos mining is unchanged. Mine on the ERG pool and ERG SOLO.
Quai – v0.55.1
Tagged August 11. The headline for miners is that go-quai now carries a built-in stratum proxy for solo mining, and the release collects a long run of work on it:
- Variable difficulty (vardiff) for the stratum proxy
- Optional PROXY protocol support, so the stratum server works behind a load balancer
- A blockTemplateUpdates websocket subscription
- Bitcoin-style difficulty values instead of raw difficulty in API submissions
- A health check service on port 8081 that compares node height against a public RPC
- Graceful stratum shutdown, unique job IDs, monotonic session IDs, and a frequency parameter that only updates ASICs at the requested rate
- KawPoW handling updates on Quai parent hash change, and guarding of the epoch and light cache DAG size
Nothing changes in your miner configuration on our side. Mine on QUAI KawPow, QUAI KawPow SOLO, QUAI SHA-256, and QUAI SHA-256 SOLO.
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