Sui Blockchain Under Scrutiny: A Deep Dive into Recent Mainnet Stability Challenges

The high-performance public blockchain, Sui, recently endured its most severe stability test since its mainnet launch. According to an incident review report published by the Sui Foundation on May 31st, the Sui mainnet experienced three distinct outages within a critical 48-hour window from May 28th to 29th. This cascade of failures was ultimately traced back to a system vulnerability introduced during a version upgrade, with each subsequent attempt at a fix inadvertently triggering the next wave of instability.

The report pinpoints a critical Gas fee calculation logic vulnerability, inadvertently activated during a recent v1.72 deployment, as the root cause. This flaw initiated a series of systemic malfunctions, leading to the mainnet’s triple paralysis over the two-day period.

Sui’s Tumultuous 48 Hours: A Timeline of Mainnet Outages

• First Outage (May 28th, ~7 AM UTC): An upgrade-induced conflict between Gas fee calculation and the asset model caused a widespread validator node crash, bringing the mainnet to a halt for nearly 7 hours.
• Second Outage (May 29th, ~5 AM UTC): A temporary hotfix patch was circumvented by a variant of the original vulnerability, plunging the mainnet into another period of paralysis for approximately 3.5 hours.
• Third Outage (May 29th, ~1:30 PM UTC): A collective validator node restart, intended to deploy a more robust fix, inadvertently triggered a long-dormant bug related to the random number state saving mechanism, resulting in nearly 6 hours of mainnet downtime.

Billing Mechanism Conflict Ignites Widespread Node Collapse

The Sui Foundation elaborated that the crisis began with the deployment of Sui’s v1.72 upgrade, which aimed to introduce a new “Address Balances” feature. However, when processing mixed payment transactions involving traditional token objects, an unforeseen and critical error was triggered.

Specifically, when a transaction was cancelled due to “insufficient funds,” the code responsible for burning Gas fees erroneously attempted to deduct funds regardless. This led to an “underflow error”—a system anomaly where a value attempts to go below zero—which subsequently caused validator nodes to crash en masse, rendering the mainnet inoperable.

To illustrate, Sui’s “token object” concept is akin to digital banknotes. A user’s SUI balance isn’t a single numerical value but rather a collection of distinct “banknotes” of varying denominations (e.g., 60, 30, and 10 SUI). When a transaction requires a fee, the network intelligently combines these “banknotes” for payment. The recent bug precisely occurred within this complex “assembly and deduction” process.

In an urgent effort to restore mainnet operations, the core development team deployed a “temporary hotfix patch” on Thursday afternoon, around 1:30 PM UTC. The team was aware that this provisional solution, while addressing the majority of the outage issues, carried a very low-probability, yet known, risk of re-triggering downtime. Prioritizing speed, the team decided to accept this calculated risk while simultaneously working on a more comprehensive, ultimate fix in the background.

However, by approximately 5 AM UTC the following morning, a specific transaction activated a “variant” of the original vulnerability. The system’s “insufficient funds” error code was overridden by another cancellation reason, effectively bypassing the previous day’s emergency patch. This led to the mainnet’s second major shutdown. Fortunately, the team swiftly completed and deployed a more robust repair program, with all validator nodes updated by around 9:40 AM UTC.

A Cascade of Errors: The Third Outage Unveiled

Frustratingly, the third outage was an unfortunate “chain collision” directly triggered by the preceding repair process. When validator nodes collectively restarted to install the ultimate fix, the participation rate for the on-chain random number protocol unexpectedly dropped below the required threshold. Following its secure design, the random number function automatically shut down to prevent potential errors.

Compounding the issue, another latent bug within the system prevented the “random number disabled” state from being successfully written to disk. Consequently, when the nodes restarted again, the system had no record that the random number function was already offline. This led to a massive backlog of transactions dependent on random numbers queuing up in the background, ultimately causing the Epoch Change (the blockchain’s periodic reallocation of validator nodes and settlement of rewards) at 1:30 PM UTC to completely stall, resulting in nearly 6 hours of downtime.

Impact and Lingering Questions for Sui’s Future

Despite the Sui Foundation’s official assurances that user assets remained secure and no confirmed transactions were rolled back, the series of consecutive outages undeniably impacted market confidence. The SUI token price briefly dipped to around $0.90, expanding its weekly decline to approximately 19%.

This marks the third significant stability incident for Sui since its mainnet went live in 2023. Previously, Sui experienced a 2-hour downtime in November 2023 due to a transaction scheduling error, and a 6-hour mainnet disruption in January 2024 caused by consensus divergence. While Sui has consistently positioned itself as a blockchain known for high throughput and performance, the painful lesson of three outages within 48 hours has undoubtedly cast a significant shadow of doubt over the network’s long-term stability and future prospects among its community and developers.