Bitcoin Unlimited Suffers Critical Bug and Node Crashes
A critical bug in Bitcoin Unlimited software causes approximately 70% of BU nodes to crash, severely damaging the project's credibility.
On March 14, 2017, Bitcoin Unlimited suffered a catastrophic software failure when a critical bug was exploited, causing approximately 70% of nodes running the software to crash simultaneously. The bug, which had been discovered by a security researcher, allowed anyone to remotely crash Bitcoin Unlimited nodes by sending them a specially crafted message.
When the vulnerability was exploited, the number of Bitcoin Unlimited nodes plummeted from nearly 800 to under 250 within hours, representing one of the most spectacular technical failures in Bitcoin's history and severely undermining Bitcoin Unlimited's credibility as an alternative to Bitcoin Core.
The bug and resulting crash dealt a devastating blow to Bitcoin Unlimited's campaign to win support for larger blocks and replace Bitcoin Core as the dominant implementation. Critics of Bitcoin Unlimited, particularly Bitcoin Core developers, had long argued that BU's development process was less rigorous and professional than Core's, and the crash provided dramatic evidence supporting that claim.
The bug existed because Bitcoin Unlimited's developers had used assertions in production code—a practice considered poor software engineering that Core developers avoided. The timing was particularly damaging as Bitcoin Unlimited had been gaining mining pool support and appeared to be building momentum toward potentially activating a contentious hard fork.
The crash caused several mining pools to reconsider their support for Bitcoin Unlimited and strengthened the position of those advocating for SegWit as a safer, more thoroughly tested scaling solution.