Monero (XMR) Hit by 18-Block Reorg in 2025: Double-Spend Fears Resurface
- What Just Happened to Monero’s Blockchain?
- Why an 18-Block Reorg Spells Trouble
- The 51% Attack Debate Reignites
- Exchange Reactions and User Safeguards
- Historical Context: Monero’s Reorg Woes
- FAQ: Your Monero Security Questions Answered
– Monero’s blockchain just endured its deepest reorganization in years, with 18 consecutive blocks rewritten in what analysts fear could be a precursor to double-spend attacks. The privacy coin’s community is now scrambling to adjust confirmation thresholds, while exchanges like BTCC monitor the situation closely.
What Just Happened to Monero’s Blockchain?
At approximately 3:42 AM UTC on September 14, Monero’s network experienced a chain reorganization so severe it rewrote 36 minutes of transaction history. Blockchain data shows two competing chains briefly coexisted before the longer chain – containing 18 new blocks – orphaned the original sequence. "This isn’t just network latency," noted BTCC analyst Mark Chen. "We’re looking at either extraordinary bad luck or intentional manipulation."
Why an 18-Block Reorg Spells Trouble
Unlike Bitcoin’s 10-minute blocks, Monero generates new blocks every 120 seconds. Here’s why the reorg matters:
- Confirmation Standard Broken: The 10-confirmation rule (20 minutes) used by merchants is now unreliable
- Double-Spend Window: Attackers could theoretically reverse transactions worth ~$2.3M (based on XMR’s $128 price)
- Mining Centralization: Data suggests 58% of recent blocks came from just two pools (Hashvault and SupportXMR)
The 51% Attack Debate Reignites
SlowMist’s Cosine raised alarms on X: "Monero’s unique PoW algorithm was supposed to prevent this. Either someone’s gaming the system, or we’ve underestimated how little hash power you actually need to disrupt the chain." CoinMarketCap data shows XMR’s hashrate dropped 19% in the 48 hours preceding the event.
Exchange Reactions and User Safeguards
Following the incident:
| Platform | Action | Confirmation Requirement |
|---|---|---|
| BTCC | Added monitoring | 25 confirmations (50 mins) |
| Kraken | Delayed withdrawals | 30 confirmations |
| LocalMonero | Paused escrow | 40 confirmations |
"I’ve advised my XMR-accepting clients to treat anything under 35 confirmations as pending," said crypto payment processor Lena Petrova. "Better safe than rugged."
Historical Context: Monero’s Reorg Woes
This isn’t Monero’s first dance with reorganization risks:
- August 2025: Qubic mining project briefly controlled 53% hashrate
- March 2024: 7-block reorg during botched miner software update
- 2021: 5-block reorg attributed to network latency
FAQ: Your Monero Security Questions Answered
How many confirmations do I need now?
Wait for at least 35 confirmations (70 minutes) for high-value transactions. Small transfers might be SAFE at 20.
Could this happen again?
Absolutely. Until Monero implements checkpointing or changes its PoW algorithm, reorgs remain possible.
Is my XMR wallet safe?
Funds are secure if you’re not actively transacting. The risk applies primarily to recent transactions.
