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A vulnerability where account data is deserialized into a Rust struct without validating that the data length, discriminator, or content matches expectations, potentially allowing an attacker to craft maliciously structured account bytes that cause undefined behavior, skip field initialization, or be misinterpreted as a different struct type. In Solana programs, using try_from_slice on data that is shorter than the expected struct silently succeeds in some configurations (or panics in others), leaving fields zeroed or corrupted. The safe pattern is to always validate the discriminator prefix, use try_from_slice_unchecked only when bounds are independently guaranteed, and leverage Anchor's automatic discriminator enforcement on Account<'info, T> deserialization.

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Unsafe Deserialization (unsafe-deserialization)
Category: Security
Definition: A vulnerability where account data is deserialized into a Rust struct without validating that the data length, discriminator, or content matches expectations, potentially allowing an attacker to craft maliciously structured account bytes that cause undefined behavior, skip field initialization, or be misinterpreted as a different struct type. In Solana programs, using try_from_slice on data that is shorter than the expected struct silently succeeds in some configurations (or panics in others), leaving fields zeroed or corrupted. The safe pattern is to always validate the discriminator prefix, use try_from_slice_unchecked only when bounds are independently guaranteed, and leverage Anchor's automatic discriminator enforcement on Account<'info, T> deserialization.
Related: Borsh, Account Data, Type Cosplay

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Branch

Borsh

Binary Object Representation Serializer for Hashing—the standard serialization format for Solana program data. Borsh produces deterministic, compact binary encodings with a fixed schema. It's used by Anchor for all account and instruction data serialization/deserialization. Borsh supports structs, enums, vectors, and other Rust types.

Serialization / Deserialization

Open term

Branch

Account Data

The byte array stored in an account that holds program-specific state. Data is typically serialized using Borsh and must be explicitly allocated at account creation. The maximum data size is 10MB. Programs are responsible for defining and managing their own data layout, including discriminators for type identification.

Account

Open term

Branch

Type Cosplay

A vulnerability, also called account confusion, where a program deserializes an account as type A when it actually contains data for type B because both structs happen to share a compatible byte layout at the fields the program checks, enabling an attacker to substitute one account type for another to satisfy access control or arithmetic that assumes a specific type. Anchor prevents this by prepending an 8-byte discriminator (the first 8 bytes of the SHA-256 hash of the fully-qualified type name) to every account during initialization and asserting it on every subsequent access; native programs must implement equivalent discriminator logic manually.

Discriminator

Open term

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Programming Model

Borsh

Binary Object Representation Serializer for Hashing—the standard serialization format for Solana program data. Borsh produces deterministic, compact binary encodings with a fixed schema. It's used by Anchor for all account and instruction data serialization/deserialization. Borsh supports structs, enums, vectors, and other Rust types.

Open term

Programming Model

Account Data

The byte array stored in an account that holds program-specific state. Data is typically serialized using Borsh and must be explicitly allocated at account creation. The maximum data size is 10MB. Programs are responsible for defining and managing their own data layout, including discriminators for type identification.

Open term

Security

Type Cosplay

A vulnerability, also called account confusion, where a program deserializes an account as type A when it actually contains data for type B because both structs happen to share a compatible byte layout at the fields the program checks, enabling an attacker to substitute one account type for another to satisfy access control or arithmetic that assumes a specific type. Anchor prevents this by prepending an 8-byte discriminator (the first 8 bytes of the SHA-256 hash of the fully-qualified type name) to every account during initialization and asserting it on every subsequent access; native programs must implement equivalent discriminator logic manually.

Open term

Security

Verifiable Build

A reproducible build process that proves deployed on-chain program bytecode was compiled from specific public source code. Tools like solana-verify use Docker containers with pinned toolchain versions to produce deterministic ELF binaries, then compare the hash of the build artifact against the deployed program data account. Verified programs are displayed with a checkmark on Solana Explorer and OtterSec's registry, increasing user trust that the running code matches the audited source.

Open term

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Programming Modelborsh

Borsh

Binary Object Representation Serializer for Hashing—the standard serialization format for Solana program data. Borsh produces deterministic, compact binary encodings with a fixed schema. It's used by Anchor for all account and instruction data serialization/deserialization. Borsh supports structs, enums, vectors, and other Rust types.

Open term

Programming Modelaccount-data

Account Data

The byte array stored in an account that holds program-specific state. Data is typically serialized using Borsh and must be explicitly allocated at account creation. The maximum data size is 10MB. Programs are responsible for defining and managing their own data layout, including discriminators for type identification.

Open term

Securitytype-cosplay

Type Cosplay

A vulnerability, also called account confusion, where a program deserializes an account as type A when it actually contains data for type B because both structs happen to share a compatible byte layout at the fields the program checks, enabling an attacker to substitute one account type for another to satisfy access control or arithmetic that assumes a specific type. Anchor prevents this by prepending an 8-byte discriminator (the first 8 bytes of the SHA-256 hash of the fully-qualified type name) to every account during initialization and asserting it on every subsequent access; native programs must implement equivalent discriminator logic manually.

Open term

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Security

Missing Signer Check

A vulnerability where a program accepts an account in a privileged role (e.g., admin, authority, payer) without verifying that the account actually signed the transaction, allowing any caller to impersonate that authority by simply passing the target pubkey as an instruction account. In native Solana programs, the check requires asserting account.is_signer == true; in Anchor, the Signer<'info> type enforces this automatically. Exploitation lets an attacker bypass all access control gated on authority equality checks, making it one of the most critical and commonly audited vulnerabilities in Solana programs.

Open term

Security

Missing Owner Check

A vulnerability where a program deserializes and trusts account data without first confirming that the account is owned by the expected program, allowing an attacker to substitute a maliciously crafted account owned by a different program whose byte layout happens to satisfy the deserialization. On Solana, every account stores a 32-byte owner field set to the program that created it; native programs must assert account.owner == &expected_program_id, while Anchor's Account<'info, T> wrapper performs this check automatically. Failure to validate ownership can lead to complete auth bypass if an attacker can construct a fake account whose data parses into a struct with elevated privileges.

Open term

Security

Arbitrary CPI

A vulnerability where a program accepts an arbitrary program account from the caller and invokes it via Cross-Program Invocation (CPI) without verifying it matches a known, trusted program ID, effectively letting an attacker substitute a malicious program that executes under the victim program's authority or manipulates accounts the victim program passes to it. A common pattern is accepting a token_program account without checking it equals spl_token::ID, so the attacker passes a lookalike program that records or drains account data. Prevention requires hard-coding or explicitly checking the program ID before every CPI call.

Open term

Security

PDA Substitution Attack

A vulnerability where a program derives a PDA internally but accepts an externally supplied account as that PDA without re-deriving and comparing the address, allowing an attacker to pass a different PDA (derived from attacker-controlled seeds) that the program will treat as legitimate. Because PDAs are deterministic, the only way to guarantee account identity is to call Pubkey::find_program_address (or equivalent) with the expected seeds inside the program and assert the result equals the supplied key. Anchor's seeds and bump constraints on the Account type automate this re-derivation and equality check.

Open term