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Security

Closing Accounts Vulnerability

A vulnerability that arises when a program closes an account by zeroing its data and transferring lamports without setting the account's discriminator or data to a sentinel closed state before the end of the instruction, leaving a window within the same transaction where other instructions can still interact with the now-empty account. The Solana runtime only removes an account from the account set when its lamports reach zero at the end of a transaction, so mid-transaction the account still exists and a subsequent instruction can re-fund it and reinstate stale data, enabling an account revival attack. Anchor's close constraint writes a CLOSED_ACCOUNT_DISCRIMINATOR (8 bytes of 0xff) and uses a force-defund mechanism to prevent resurrection.

IDclosing-accounts
Plain meaning

Plain meaning

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A vulnerability that arises when a program closes an account by zeroing its data and transferring lamports without setting the account's discriminator or data to a sentinel closed state before the end of the instruction, leaving a window within the same transaction where other instructions can still interact with the now-empty account. The Solana runtime only removes an account from the account set when its lamports reach zero at the end of a transaction, so mid-transaction the account still exists and a subsequent instruction can re-fund it and reinstate stale data, enabling an account revival attack. Anchor's close constraint writes a CLOSED_ACCOUNT_DISCRIMINATOR (8 bytes of 0xff) and uses a force-defund mechanism to prevent resurrection.

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Closing Accounts Vulnerability (closing-accounts)
Category: Security
Definition: A vulnerability that arises when a program closes an account by zeroing its data and transferring lamports without setting the account's discriminator or data to a sentinel closed state before the end of the instruction, leaving a window within the same transaction where other instructions can still interact with the now-empty account. The Solana runtime only removes an account from the account set when its lamports reach zero at the end of a transaction, so mid-transaction the account still exists and a subsequent instruction can re-fund it and reinstate stale data, enabling an account revival attack. Anchor's close constraint writes a CLOSED_ACCOUNT_DISCRIMINATOR (8 bytes of 0xff) and uses a force-defund mechanism to prevent resurrection.
Related: Close Account, Rent, Account Revival Attack
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Branch

Close Account

The process of reclaiming an account's lamports and marking it for deletion. To close an account: transfer all lamports to a recipient, zero out the data, and (in Anchor) set the discriminator to a closed sentinel. The runtime garbage-collects zero-lamport accounts. Failing to zero data enables revival attacks.

LamportAccount
Open term
Branch

Rent

A fee mechanism that charges accounts for storing data on-chain. Accounts must maintain a minimum lamport balance proportional to their data size (~6.96 SOL per MB) to be rent-exempt. Since 2022, all new accounts must be rent-exempt at creation. Accounts falling below the threshold are removed during rent collection.

Rent Exemption
Open term
Branch

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
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Programming Model

Close Account

The process of reclaiming an account's lamports and marking it for deletion. To close an account: transfer all lamports to a recipient, zero out the data, and (in Anchor) set the discriminator to a closed sentinel. The runtime garbage-collects zero-lamport accounts. Failing to zero data enables revival attacks.

Open term
Programming Model

Rent

A fee mechanism that charges accounts for storing data on-chain. Accounts must maintain a minimum lamport balance proportional to their data size (~6.96 SOL per MB) to be rent-exempt. Since 2022, all new accounts must be rent-exempt at creation. Accounts falling below the threshold are removed during rent collection.

Open term
Security

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
Security

Denial of Service (DoS)

A class of attacks that prevent legitimate users from successfully executing transactions against a Solana program, either by exhausting the compute budget (e.g., triggering O(n) iteration over an unbounded on-chain list to force CU exhaustion), filling an account's allocated space to block appends, or exploiting program logic to cause systematic transaction failure. On Solana, each transaction has a compute budget cap of 1.4 million CUs by default (extendable to 1.4 million via ComputeBudgetInstruction), so programs that loop over caller-controlled data sizes are vulnerable. Mitigations include bounding all on-chain collections, paginating iteration, and preferring off-chain indexing over on-chain enumeration.

Open term
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Securityduplicate-mutable-accounts

Duplicate Mutable Accounts

A vulnerability where the same account is passed twice in the accounts list for a single instruction under different argument names, and the program writes to what it believes are two independent accounts, with the second write silently overwriting the first on the single underlying account in the runtime's account map. For example, if from and to in a transfer handler reference the same key, debiting from and crediting to nets out to a free credit. In native programs the check requires comparing account keys; Anchor automatically detects duplicate mutable accounts and returns an error when the same pubkey appears more than once in writable positions within a single instruction's account list.

Open term
Securityremaining-accounts

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
Securityvulnerability-disclosure

Vulnerability Disclosure

Process of responsibly reporting security flaws to affected parties before public disclosure. Solana has a bug bounty program through Immunefi, and most major protocols maintain responsible disclosure policies. Coordinated disclosure gives teams time to patch vulnerabilities before exploitation.

Open term
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Programming Modelclose-account

Close Account

The process of reclaiming an account's lamports and marking it for deletion. To close an account: transfer all lamports to a recipient, zero out the data, and (in Anchor) set the discriminator to a closed sentinel. The runtime garbage-collects zero-lamport accounts. Failing to zero data enables revival attacks.

Open term
Programming Modelrent

Rent

A fee mechanism that charges accounts for storing data on-chain. Accounts must maintain a minimum lamport balance proportional to their data size (~6.96 SOL per MB) to be rent-exempt. Since 2022, all new accounts must be rent-exempt at creation. Accounts falling below the threshold are removed during rent collection.

Open term
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
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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