CVE-2025-54070: 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(byte...

Description

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.

Metrics

CVSS 4.0

6.9/10

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS Probability

0.33%

25.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-125

References

Timeline

Published: Jul 17, 2025
Last Modified: Jun 17, 2026
Status: Deferred

Frequently Asked Questions

What is CVE-2025-54070?

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.

How severe is CVE-2025-54070?

CVE-2025-54070 has a CVSS score of 6.9/10 (MEDIUM severity). The EPSS model estimates a 0.33% probability of exploitation in the next 30 days.

How do I fix CVE-2025-54070?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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