Get the Crypto Payment Security & Compliance Playbook
Back to Blog

New Integer Overflow Bug Discovered in Solana rBPF

Code Auditing
December 30, 2021

Recently, our vulnerability detection system discovered a critical issue in the rBPF of Solana (i.e., the virtual machine where all the Solana dApps are running on: https://github.com/solana-labs/rbpf). After a careful investigation, we found that it is an integer overflow bug which can be exploited to crash down the whole Solana network. We have reported the bug to the Solana security team, and the team immediately sprang into action to confirm and fix the bug. As of this writing, almost all the validator nodes received the patch and upgraded to the latest version, which means it is safe to make a public disclosure.

eBPF and rBPF

Extended Berkeley Packet Filter (eBPF[1]) is initially developed for filtering packets in the kernel. Due to the security, efficiency, and scalability of eBPF, it is now used in various areas like networking, tracing, profiling, etc[2]. Considering the rich capability of eBPF, Solana choose it as the execution engine for the smart contract as well. To build the dApps on Solana, developers need to develop their smart contracts in Rust that will be compiled into eBPF bytecode.

To host the dApps of Solana, a precise virtual machine for eBPF is required. In this case, Solana uses the rBPF, which is a virtual machine for eBPF written in Rust. However, whether the proposed virtual machine (i.e., rBPF) is robust, secure, and precise is unknown. Once there exist security issues inside the rBPF, all the validators containing the rBPF can be influenced, resulting in huge loss (e.g., DDoS attack) for the whole Solana network.

The root cause of the bug

We have developed a tool to locate the bugs for the rBPF. This tool is still under the active development. During this process, one serious problem was identified in rBPF (version 0.2.16), which can take down the whole network.

Specifically, function “load” in file “elf.rs” is used to parse and verify the ELF file (the smart contract). First, function “load” would read the ELF structure and invoke function “relocate” to set up the callee offset. However, in function “relocate”, the attribute “sym.st_value” is retrieved from the ELF file directly . If the “st_value” is large enough, integer overflow could be triggered when calculating the “addr”, which is the sum-up of “sym.st_value” and “refd_pa”.

In this case, an attacker can create a malicious ELF file as a smart contract, which can trigger the integer overflow. After that, every validator would run the target ELF file and the rBPF would get panic with “add with overflow”.

At this moment, rBPF will get stuck and the coming transactions will not be executed, resulting in a DoS attack. We can observe that the node get stuck at “Finalizing transaction”, which is shown in the following, due to the integer overflow while loading the ELF file.

This issue was introduced in https://github.com/solana-labs/rbpf/pull/200, meaning the rBPF is vulnerable from version 0.2.14. We identified the issue and reported it to the Solana security team on 2021 December 6th. Solana fixes the issue in a few hours by using the safemath mechanism after our report. The fix is in https://github.com/solana-labs/rbpf/pull/236. At the time of writing (2021/12/30), more than 86% of the validators have upgraded to the newest version.

[1] https://en.wikipedia.org/wiki/Berkeley_Packet_Filter

[2] https://ebpf.io/

Timeline

  • 2021/12/06: the problem was reported to the Solana security team
  • 2021/12/06: the vulnerability was fixed.
  • 2021/12/30: the information of this vulnerability was released
  • 2022/01/28: the CVE-2021–46102 was assigned
Sign up for the latest updates
~$11.3M Lost: Multicall Router, Nostra | BlockSec Weekly
Security Insights

~$11.3M Lost: Multicall Router, Nostra | BlockSec Weekly

This report, covering 2026/09/14 - 2026/09/20, examines two security incidents with approximately $11.3M in combined losses, on Ethereum and Starknet. In the larger one, a multicall router accepted its own address as a dispatch target, so the nested call reached the Gateway module of a Safe wallet carrying the router's own already-authorized identity instead of the external caller's, and roughly 2,900 `aEthrsETH` was routed out of that wallet into an attacker-created Uniswap v4 pool. On Starknet, Nostra's oracle integration required a minimum of only one aggregated source, so when only two of the three configured price sources reached the aggregation, a manipulated thin-pool quote averaged with a normal quote to value `NSTR` at roughly $49.52, supporting approximately $3.5M of borrowing against overvalued collateral.

~$320M Lost: Liquid Network, Symbiosis Exploits | BlockSec
Security Insights

~$320M Lost: Liquid Network, Symbiosis Exploits | BlockSec

This report, covering 2026/09/07 - 2026/09/13, examines two security incidents that caused approximately $320M in losses, including the Liquid Network exploit of 2026/09/06 that the previous report did not cover. The larger was that Liquid Network exploit, where the rangeproof validation cache in Elements derived its key by hashing four fields — two of them variable in length — concatenated with nothing marking the boundaries between them, so a verdict recorded for one output was returned for another whose proof was never examined, letting the attacker create 4,000 unbacked L-BTC and peg out nearly all of them as bitcoin. On the Bitcoin route of the Symbiosis cross-chain bridge, spanning BNB Smart Chain, Ethereum and Rootstock, off-chain code that reads Bitcoin deposits took the depositor's identity from a field the depositor controls and then subtracted its fee from the deposit without checking whether the fee itself was negative, letting a 330-satoshi deposit mint `46,116,860,184.27388234 syBTC`; the pools it had to be sold through held only 11.26 syBTC, so the loss to liquidity providers and users came to an estimated 9.97 BTC (~$770K).

~$9.4M Lost: Injective, Aquifer Exploits | BlockSec Weekly
Security Insights

~$9.4M Lost: Injective, Aquifer Exploits | BlockSec Weekly

During the past week (2026/08/31 - 2026/09/06), four security incidents caused approximately $9.4M in losses across Injective, Solana, Ethereum, and Flow EVM. The largest was the Injective exploit, where an insurance fund identifier collided with a binary options market identifier and the settlement path never compared their denominations, draining about $4.8M; Aquifer on Solana lost about $2.47M because its swap path invoked an unvalidated caller-supplied Token Program, and Notional Finance V1 on Ethereum lost about $1.73M to an unchecked `uint128` cast that valued a debt at zero. Ankr FLOW on Flow EVM closed out the week with about $410K drained through a staking entry point that skipped its pause guard and minted against a stale ratio.

Best Security Auditor for Web3

Validate design, code, and business logic before launch. Aligned with the highest industry security standards.

BlockSec Audit