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Litecoin says its 13-block reorg was not a ‘zero-day, but GitHub commit history shows otherwise
Litecoin’s foundation called the weekend exploit a zero-day. The litecoin-project GitHub repository shows the consensus vulnerability was privately patched between March 19 and 26, more than four weeks before the attack.
Apr 26, 2026, 8:34 a.m.
What to know:
- Attackers exploited a previously patched but not fully deployed vulnerability in Litecoin’s Mimblewimble Extension Block protocol, triggering a 13-block chain reorganization that rewound about 32 minutes of activity.
- Public GitHub commits show the core consensus bug was privately fixed weeks before the exploit, creating a window in which some mining pools ran updated code while others remained vulnerable, a gap researchers say the attackers appeared to target.
- The Litecoin network ultimately reorganized back to the valid chain once denial-of-service attacks on patched miners ceased, but the foundation has not yet explained the patch timeline or disclosed how much LTC was affected during the invalid block window.
Litecoin Core v0.21.5.4 released! All users are advised to upgrade. This release contains important security updates. https://t.co/6vtrhdXi4c
— Litecoin (@litecoin) April 25, 2026
The Foundation said in Asian morning hours on Sunday the bug was fully patched and the network is operating normally.
However, prominent researchers say the litecoin-project GitHub repository tells a different story. Security researcher bbsz, who works with the SEAL911 emergency response group for crypto exploits, posted the patch timeline pulled from the public commit log.
