OpenZeppelin openzeppelin-contracts up to 5.3.x Bytes.sol lastIndexOf Pos out-of-bounds

Summaryinfo

A vulnerability marked as problematic has been reported in OpenZeppelin openzeppelin-contracts up to 5.3.x. The affected element is the function lastIndexOf in the library Bytes.sol. The manipulation of the argument Pos leads to out-of-bounds. This vulnerability is uniquely identified as CVE-2025-54070. The attack is possible to be carried out remotely. No exploit exists. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in OpenZeppelin openzeppelin-contracts up to 5.3.x. It has been rated as critical. This issue affects the function lastIndexOf in the library Bytes.sol. The manipulation of the argument pos with an unknown input leads to a out-of-bounds vulnerability. Using CWE to declare the problem leads to CWE-125. The product reads data past the end, or before the beginning, of the intended buffer. Impacted is integrity, and availability. The summary by CVE is:

OpenZeppelin Contracts is a library for secure smart contract development. Starting in version 5.2.0 and prior to version 5.4.0, the `lastIndexOf(bytes,byte,uint256)` function of the `Bytes.sol` library may access uninitialized memory when the following two conditions hold: 1) the provided buffer length is empty (i.e. `buffer.length == 0`) and position is not `2**256 - 1` (i.e. `pos != type(uint256).max`). The `pos` argument could be used to access arbitrary data outside of the buffer bounds. This could lead to the operation running out of gas, or returning an invalid index (outside of the empty buffer). Processing this invalid result for accessing the `buffer` would cause a revert under normal conditions. When triggered, the function reads memory at offset `buffer + 0x20 + pos`. If memory at that location (outside the `buffer`) matches the search pattern, the function would return an out of bound index instead of the expected `type(uint256).max`. This creates unexpected behavior where callers receive a valid-looking index pointing outside buffer bounds. Subsequent memory accesses that don't check bounds and use the returned index must carefully review the potential impact depending on their setup. Code relying on this function returning `type(uint256).max` for empty buffers or using the returned index without bounds checking could exhibit undefined behavior. Users should upgrade to version 5.4.0 to receive a patch.

The advisory is shared at github.com. The identification of this vulnerability is CVE-2025-54070 since 07/16/2025. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details are known, but no exploit is available.

Upgrading to version 5.4.0 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2025-21789). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Vendor

• OpenZeppelin

Name

• openzeppelin-contracts

Version

• 5.0
• 5.1
• 5.2
• 5.3

Website

• Product: https://github.com/OpenZeppelin/openzeppelin-contracts/

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CPE 2.2info

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Entryinfo

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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