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Security

Reinitialization Attack

A vulnerability where a program allows an already-initialized account to be initialized a second time, overwriting its state — including authority or ownership fields — with attacker-supplied data, effectively letting the attacker seize control of an existing account without going through normal privilege checks. The canonical defense is storing an is_initialized boolean or an Anchor discriminator in the account and asserting it is false (or that the discriminator is unset) at the start of every initialization instruction; Anchor's init constraint enforces this by failing if the account's discriminator is already non-zero.

IDreinitialization
Plain meaning

Plain meaning

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A vulnerability where a program allows an already-initialized account to be initialized a second time, overwriting its state — including authority or ownership fields — with attacker-supplied data, effectively letting the attacker seize control of an existing account without going through normal privilege checks. The canonical defense is storing an is_initialized boolean or an Anchor discriminator in the account and asserting it is false (or that the discriminator is unset) at the start of every initialization instruction; Anchor's init constraint enforces this by failing if the account's discriminator is already non-zero.

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Reinitialization Attack (reinitialization)
Category: Security
Definition: A vulnerability where a program allows an already-initialized account to be initialized a second time, overwriting its state — including authority or ownership fields — with attacker-supplied data, effectively letting the attacker seize control of an existing account without going through normal privilege checks. The canonical defense is storing an is_initialized boolean or an Anchor discriminator in the account and asserting it is false (or that the discriminator is unset) at the start of every initialization instruction; Anchor's init constraint enforces this by failing if the account's discriminator is already non-zero.
Related: Account, Discriminator
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Branch

Account

The fundamental data storage unit on Solana. Every piece of state is stored in an account identified by a 32-byte public key. Accounts hold a lamport balance, an owner program, a data byte array (up to 10MB), and an executable flag. Only the owning program can modify an account's data, but anyone can credit lamports to it.

Public Key (Pubkey)Lamport
Open term
Branch

Discriminator

An 8-byte identifier prepended to account data and instruction data to distinguish types. Anchor computes it as the first 8 bytes of `sha256('account:<AccountName>')` for accounts and `sha256('global:<function_name>')` for instructions. Discriminators prevent type cosplay attacks by ensuring data is deserialized as the correct type.

Anchor FrameworkInstruction
Open term
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Programming Model

Account

The fundamental data storage unit on Solana. Every piece of state is stored in an account identified by a 32-byte public key. Accounts hold a lamport balance, an owner program, a data byte array (up to 10MB), and an executable flag. Only the owning program can modify an account's data, but anyone can credit lamports to it.

Open term
Programming Model

Discriminator

An 8-byte identifier prepended to account data and instruction data to distinguish types. Anchor computes it as the first 8 bytes of `sha256('account:<AccountName>')` for accounts and `sha256('global:<function_name>')` for instructions. Discriminators prevent type cosplay attacks by ensuring data is deserialized as the correct type.

Open term
Security

Remaining Accounts Misuse

A vulnerability arising from the use of ctx.remaining_accounts in Anchor (or unchecked trailing accounts in native programs), where accounts passed beyond the explicitly declared account struct are not subject to any automatic owner, signer, or constraint checks, leaving it entirely to the program to validate them. Attackers can exploit this by injecting unexpected accounts — fake mints, unauthorized signers, or accounts owned by a malicious program — that the program then treats as trusted inputs. Programs using remaining_accounts must manually verify every account's key, owner, is_signer, and is_writable properties before use, making this pattern a frequent audit finding.

Open term
Security

Reentrancy Guard

A protective pattern that prevents a program from being invoked recursively through cross-program invocations, mitigating reentrancy attacks. While the Solana runtime inherently prevents direct same-program reentrancy (a program cannot CPI into itself), indirect reentrancy through shared mutable accounts via third-party programs is still possible. Reentrancy guards typically use a flag in account state that is set at instruction entry and cleared at exit, causing reentrant calls to fail. Less critical on Solana than on EVM chains due to the runtime's built-in protection.

Open term
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Securityrevival-attack

Account Revival Attack

An exploit that resurrects an account that a program has logically closed within the same transaction by sending lamports back to it before the transaction finalizes, causing its on-chain data — which was never securely wiped — to re-appear as a funded, seemingly valid account in future transactions. Because the Solana runtime keeps an account alive as long as it holds any lamports, transferring even 1 lamport back to a closed-but-not-wiped account prevents its deletion and allows an attacker to reuse its stale state. The defense is to explicitly overwrite account data with a closed discriminator and to use force-defund patterns so any lamports transferred in during the same transaction are immediately drained.

Open term
Securityflash-loan-attack

Flash Loan Attack

An exploit where an attacker borrows a large amount of tokens via an uncollateralized flash loan, uses the borrowed funds to manipulate protocol state (typically distorting oracle prices or satisfying collateral requirements), extracts profit from the manipulated state, and repays the loan — all within a single atomic transaction. On Solana, flash loans are possible because transactions are atomic: if any instruction fails, the entire transaction reverts including the loan. Defenses include using time-weighted oracle prices, enforcing borrowing caps, and requiring multi-slot settlement.

Open term
Securityinstruction-ordering-attack

Instruction Ordering Attack

Exploit where an attacker crafts a transaction with instructions in a specific order to manipulate program state between instructions within the same transaction. Since Solana executes all instructions in a transaction sequentially, earlier instructions can modify account state that later instructions depend on, enabling unexpected state transitions.

Open term
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Programming Modelaccount

Account

The fundamental data storage unit on Solana. Every piece of state is stored in an account identified by a 32-byte public key. Accounts hold a lamport balance, an owner program, a data byte array (up to 10MB), and an executable flag. Only the owning program can modify an account's data, but anyone can credit lamports to it.

Open term
Programming Modeldiscriminator

Discriminator

An 8-byte identifier prepended to account data and instruction data to distinguish types. Anchor computes it as the first 8 bytes of `sha256('account:<AccountName>')` for accounts and `sha256('global:<function_name>')` for instructions. Discriminators prevent type cosplay attacks by ensuring data is deserialized as the correct type.

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