2026 Vue d'ensemble de la sécurité des ponts inter-chaînes : types de vulnérabilités et analyse des architectures à haut risque

Cross-chain bridges are becoming the most severe attack targets for capital loss within the DeFi ecosystem. By early 2026, the total amount stolen from cross-chain bridges has exceeded $2.8 billion, accounting for nearly 40% of all stolen assets in Web3. In February 2026 alone, security incidents in the crypto space caused approximately $228 million in total losses, with attacks related to cross-chain bridges continuing to dominate.

These attacks do not occur randomly. Sherlock’s early 2026 report on cross-chain security pointed out that, in 2026, vulnerabilities in cross-chain systems still follow predictable patterns: trust assumptions are embedded as security guarantees in code, message boundary authentication fails, and systems grant full permissions via single execution paths.

2026 Key Features of Cross-Chain Attacks

In 2026, cross-chain attacks no longer aim solely for the sensational “draining large amounts of funds in one go,” but instead show fragmentation, high frequency, and complexity. The attack surface has expanded from simple smart contract code vulnerabilities to broader dimensions such as key management, operational security, and cross-chain message verification logic.

From macro data, the total hacker attack losses in DeFi during the first quarter of 2026 were about $168 million, a significant decrease from approximately $1.58 billion in the same period in 2025, but the structural risks of cross-chain bridges have not been fundamentally alleviated. Among the lost funds, access control vulnerabilities remain the main cause of major asset losses, accounting for over 60% of total losses.

Meanwhile, the evolution of attack methods is accelerating. Security research indicates that in 2026, smart contracts face emerging threats such as AI-driven automated vulnerability discovery, cross-chain bridge exploits, and quantum computing risks. Attackers use machine learning to identify zero-day vulnerabilities at a rate far exceeding previous levels. The reason why cross-chain bridges continue to be high-frequency targets is fundamentally because: the security model of cross-chain systems inherently depends on the precise implementation of multi-party trust assumptions, and any deviation can lead to systemic collapse.

Four Major Vulnerability Types Fully Analyzed

Missing Input Validation: The Most Basic Yet Deadly Vulnerability

In OWASP’s 2026 classification of smart contract security risks, missing input validation is listed as an independent risk category. It describes situations where smart contracts fail to strictly enforce data formats, boundaries, and authorization checks when processing external data—such as function parameters, cross-chain messages, or signature payloads.

The Hyperbridge attack is a typical example of this type of vulnerability. On April 13, 2026, attackers exploited the lack of validation for the condition leaf_index < leafCount in the VerifyProof() function of Hyperbridge’s HandlerV1 contract. After forging a Merkle proof, they executed the ChangeAssetAdmin operation via the TokenGateway path, gaining admin and minting rights for the wrapped DOT contract on Ethereum. Subsequently, the attacker minted 1 billion fake bridged DOT tokens and sold them en masse, profiting approximately $237,000.

Another typical case is the CrossCurve cross-chain bridge attack. In February 2026, attackers exploited a gateway verification bypass vulnerability in the expressExecute function of the ReceiverAxelar contract. They falsely believed the payload was a legitimate cross-chain instruction, and in the absence of corresponding deposits on the source chain, stole about $3 million worth of assets. The essence of this vulnerability is also a failure in input validation logic—the contract did not strictly verify the caller’s identity and message source.

Replay Attacks and Proof Verification Flaws

Replay attacks are a recurring vulnerability pattern in cross-chain bridges. Their typical feature is: attackers intercept or reuse legitimate cross-chain message proofs from the past, binding them to newly crafted malicious requests, thus bypassing replay protection mechanisms.

In the Hyperbridge incident, BlockSec Phalcon characterized the vulnerability as an MMR (Merkle Mountain Range) proof replay flaw. The contract’s replay protection only verified whether the hash of the request commitment had been used before, but the proof verification process did not bind the submitted request payload to the proof being validated. As a result, attackers could replay a previously accepted valid proof and pair it with a new malicious request, successfully altering permissions.

It is worth noting that this is not the first occurrence of similar methods. Previously, an attack using the same technique targeted MANTA and CERE tokens, resulting in losses of about $12,000. This indicates that this vulnerability pattern is transferable—any cross-chain protocol using similar message verification architectures that do not strictly check the binding between proof and payload may face similar threats.

At the academic level, the COBALT-TLA research team pointed out that exploits of cross-chain bridge vulnerabilities have caused losses exceeding $1.1 billion. The recurring root cause is the violation of temporal ordering in distributed state machines. The common features of the three major historical exploits—Ronin (about $625 million), Wormhole (about $320 million), and Nomad (about $190 million)—are not cryptographic failures or arithmetic overflows, but violations of temporal ordering and failures in distributed state synchronization.

Access Control Failures and Permission Management Vulnerabilities

Access control vulnerabilities describe situations where smart contracts fail to strictly enforce who can invoke privileged actions, under what conditions, and with what parameters. In cross-chain bridges, this vulnerability is especially destructive.

The ioTube cross-chain bridge incident is a typical case of access control failure. Attackers gained control of the Ethereum validator owner’s private key, successfully infiltrated the bridge contract, and caused losses exceeding $4.4 million. This incident reveals a key fact: even well-audited code can be compromised due to weak key management. Security experts point out that such incidents are essentially operational security failures, not external smart contract vulnerabilities—under the threat model of 2026, key and signature operation failures under pressure have become recurring failure modes.

The Balancer V2 incident (loss of about $128 million) also confirms this. Its pool configuration and ownership assumptions contained access control flaws—critical pool operations must be guarded by explicit role checks, and any “owner” concept across chains must be verified on-chain, not assumed from message sources.

Economic Attacks and Liquidity Risks

Beyond traditional technical vulnerabilities, 2026 also saw a new class of attacks—economic attacks. These do not rely on code flaws but exploit protocol economic models and incentive mechanisms to arbitrage or manipulate.

Sherlock’s report indicates that rapid cross-chain and composability have elevated economic attacks (MEV, timing manipulations) and systemic risks (bridged assets as DeFi primitives) to threats comparable to traditional forgery attacks.

Academic research in February 2026 introduced a new attack category called “liquidity exhaustion attacks.” In intent-based cross-chain bridges, solvers pre-provide liquidity to immediately fulfill user cross-chain orders. Researchers proposed a replay-based parameterized attack simulation framework, revealing that such attacks can cause solvers’ liquidity to be systematically exhausted in a short period.

The emergence of this attack type implies that cross-chain bridge security is no longer just a code audit issue but also a protocol design and economic incentive problem. A technically secure cross-chain bridge can still suffer significant losses under certain market conditions due to liquidity design flaws.

High-Risk Architectures: Four Trust Models and Their Security Boundaries

The security of cross-chain bridges heavily depends on their underlying trust architecture. Sherlock classifies cross-chain message verification mechanisms into four families, each corresponding to different trust assumptions and failure modes.

Light Client Verification. The target chain verifies the source chain’s consensus or finality rules via light clients or equivalent verifiers, accepting messages anchored to the source chain supported by proofs. The promise is “trust from verification,” but risks include finality mismatches, verifier vulnerabilities, censorship leading to liveness loss, and improper behavior handling.

Committee or External Proofs. Trust is based on signatures reaching a threshold—multi-signature schemes, MPC sets, guardians, or validator committees. The design is simple and fast, but trust assumptions are “enough honest signers”—if signers are compromised, the system is vulnerable. The private key leak in ioTube is a typical failure case.

Optimistic Verification. Default acceptance of claims, with a window for disputes—usually with deposits and dispute paths. The trust assumption is more subtle: at least one honest observer remains online during the window, has sufficient funds, and can submit disputes on-chain. The key change in 2026 is that delays and malicious interference can be as destructive as forgery.

Zero-Knowledge Validity Cross-Chain Bridges. Trust is based on succinct validity proofs—provers demonstrate state transitions on the source chain, and the target chain verifies the proof. Theoretically offering the highest security, but the computational cost of proof generation and circuit security remain practical challenges.

2026 Cross-Chain Bridge Security Risk Quick Reference

Below is a summary of the core knowledge framework of current cross-chain bridge security from vulnerability types, technical performance, and protective strategies:

From Vulnerability Identification to Risk Mitigation: Dual Defense for Users and Developers

For ordinary users, completely avoiding cross-chain bridge risks is unrealistic, but the following can significantly reduce exposure:

Understanding the “Dual-layer Risk” of Bridged Assets. Holding bridged tokens entails risks on both chains and the bridge contract itself. The Hyperbridge incident clarified that the vulnerability only affected the bridged version of DOT on Ethereum, not native DOT or other assets in the Polkadot ecosystem. Users must recognize that the security boundary of bridged assets is not equivalent to native assets.

Pay Attention to Security Architecture Differences. Not all cross-chain bridges face the same level of risk. Bridges based on light client verification generally offer stronger security guarantees than those relying on external validator sets, but implementation flaws can still expose vulnerabilities. Users should understand the verification mechanism type and its historical security record.

Avoid Long-term Storage of Large Assets on Bridges. Using cross-chain bridges as “transfer channels” rather than “storage facilities” is the simplest defense. After completing cross-chain operations, assets should be transferred promptly to native wallets or trusted smart contracts on the target chain.

Maintain Continuous Awareness of Security Developments. Users can regularly monitor real-time alerts from security agencies like CertiK, BlockSec, and PeckShield, and stay sensitive to protocol vulnerabilities related to their assets.

For developers, the OWASP 2026 smart contract security risk classification provides a systematic protection framework: enforce strict access controls and role separation (SC01), validate all external inputs (SC05), and verify payload sizes for cross-chain messages (SCWE-087). Incorporating formal verification tools (such as TLA+ model checking) to systematically verify the temporal logic of cross-chain protocols has become standard among top projects.

Conclusion

The security landscape of cross-chain bridges in 2026 reveals a core paradox: as interoperability demands explode—top ten cross-chain routes handled over $41 billion in 10 months in 2024, and the interoperability market is projected to reach $2.56 billion by 2030—the security of cross-chain infrastructure has not kept pace.

From Hyperbridge’s MMR proof replay flaw to CrossCurve’s input validation failure, from ioTube’s private key leak to Ronin’s ordering violation, attack patterns are diverse but share a common underlying logic: deviations in trust assumptions are precisely exploited by attackers, transforming into permission gains via single execution paths. Building secure cross-chain bridges requires comprehensive upgrades—from code auditing, trust assumption modeling, economic design, to formal verification. Only by shifting security from reactive “patching” to proactive “validation” can cross-chain bridges truly evolve from Web3’s Achilles’ heel into a reliable value transfer layer.