Glossary OS

Plain meaning

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A Solana program whose upgrade authority has been set to None, permanently preventing any future bytecode changes. Once a program is made immutable, its on-chain code can never be modified, providing the strongest guarantee to users that the program logic they interact with will not change. Immutability is achieved by invoking the Upgradeable BPF Loader's SetAuthority instruction with None. This is irreversible and should only be done after thorough auditing and testing.

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Immutable Program (immutable-program)
Category: Security
Definition: A Solana program whose upgrade authority has been set to None, permanently preventing any future bytecode changes. Once a program is made immutable, its on-chain code can never be modified, providing the strongest guarantee to users that the program logic they interact with will not change. Immutability is achieved by invoking the Upgradeable BPF Loader's SetAuthority instruction with None. This is irreversible and should only be done after thorough auditing and testing.
Related: Upgrade Authority, Upgradeable BPF Loader, Verifiable Build

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Branch

Upgrade Authority

The pubkey authorized to upgrade a program's bytecode via the Upgradeable BPF Loader. Only the upgrade authority can deploy new bytecode to the program data account. Setting the upgrade authority to None makes the program immutable. Multisig (e.g., Squads) is commonly used to manage upgrade authority for production programs.

Program

Open term

Branch

Upgradeable BPF Loader

The current BPF Loader (BPFLoaderUpgradeab1e111...) that supports deploying and upgrading programs. It creates three accounts: the program account (thin proxy with executable flag), the program data account (holds the actual ELF bytecode), and records the upgrade authority. Programs can be made immutable by setting the authority to None.

BPF Loader Program Data Account

Open term

Branch

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.

Solana Verify (solana-verifiable-build)Security Audit

Open term

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Programming Model

Upgrade Authority

The pubkey authorized to upgrade a program's bytecode via the Upgradeable BPF Loader. Only the upgrade authority can deploy new bytecode to the program data account. Setting the upgrade authority to None makes the program immutable. Multisig (e.g., Squads) is commonly used to manage upgrade authority for production programs.

Open term

Programming Model

Upgradeable BPF Loader

The current BPF Loader (BPFLoaderUpgradeab1e111...) that supports deploying and upgrading programs. It creates three accounts: the program account (thin proxy with executable flag), the program data account (holds the actual ELF bytecode), and records the upgrade authority. Programs can be made immutable by setting the authority to None.

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

Security

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

Related terms

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Programming Modelupgrade-authority

Upgrade Authority

The pubkey authorized to upgrade a program's bytecode via the Upgradeable BPF Loader. Only the upgrade authority can deploy new bytecode to the program data account. Setting the upgrade authority to None makes the program immutable. Multisig (e.g., Squads) is commonly used to manage upgrade authority for production programs.

Open term

Programming Modelupgradeable-loader

Upgradeable BPF Loader

The current BPF Loader (BPFLoaderUpgradeab1e111...) that supports deploying and upgrading programs. It creates three accounts: the program account (thin proxy with executable flag), the program data account (holds the actual ELF bytecode), and records the upgrade authority. Programs can be made immutable by setting the authority to None.

Open term

Securityverifiable-build

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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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