GHSA-2pgj-5cv2-6xxw
FuelVM is vulnerable to heap memory allocation re-use bug
Impact
A memory safety vulnerability was present in the Fuel Virtual Machine (FuelVM), where memory reads could bypass expected access controls. Specifically, when a smart contract performed a mload (or other opcodes which access memory) on memory that had been deallocated using ret, it was still able to access the old memory contents. This occurred because the memory region was not zeroed out or otherwise marked as invalid. As a result, smart contracts could potentially read sensitive data left over from other contracts if the same memory was reallocated, violating isolation guarantees between contracts and enabling unintended data leakage.
All users running affected versions of FuelVM that relied on strict memory isolation between smart contracts were impacted.
Patches
The vulnerability was patched by modifying the FuelVM to ensure that memory deallocated with ret was zeroed out or made inaccessible. The fix was included in FuelVM version v0.60.1 and back-ported to v0.59.3. This patch was released to the Fuel network on Friday, April 18th, 2025.
Workarounds
There were no reliable workarounds that fully mitigated the vulnerability. While developers could manually zero out sensitive memory regions before returning from a function, this approach was error-prone and could not be enforced at the VM level. Upgrading to a patched version remained the recommended course of action.
References
- Fix implemented in the FuelVM GitHub repository (https://github.com/FuelLabs/fuel-vm/pull/941)
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- None
- Availability
- None
What each source reports
GitHub Advisories Score used
FuelVM is vulnerable to heap memory allocation re-use bug
Impact
A memory safety vulnerability was present in the Fuel Virtual Machine (FuelVM), where memory reads could bypass expected access controls. Specifically, when a smart contract performed a mload (or other opcodes which access memory) on memory that had been deallocated using ret, it was still able to access the old memory contents. This occurred because the memory region was not zeroed out or otherwise marked as invalid. As a result, smart contracts could potentially read sensitive data left over from other contracts if the same memory was reallocated, violating isolation guarantees between contracts and enabling unintended data leakage.
All users running affected versions of FuelVM that relied on strict memory isolation between smart contracts were impacted.
Patches
The vulnerability was patched by modifying the FuelVM to ensure that memory deallocated with ret was zeroed out or made inaccessible. The fix was included in FuelVM version v0.60.1 and back-ported to v0.59.3. This patch was released to the Fuel network on Friday, April 18th, 2025.
Workarounds
There were no reliable workarounds that fully mitigated the vulnerability. While developers could manually zero out sensitive memory regions before returning from a function, this approach was error-prone and could not be enforced at the VM level. Upgrading to a patched version remained the recommended course of action.
References
- Fix implemented in the FuelVM GitHub repository (https://github.com/FuelLabs/fuel-vm/pull/941)
- Record
GHSA-2pgj-5cv2-6xxw- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N - Weakness
- CWE-416
- Updated
- 2026-11-02
OSV
FuelVM is vulnerable to heap memory allocation re-use bug
Impact
A memory safety vulnerability was present in the Fuel Virtual Machine (FuelVM), where memory reads could bypass expected access controls. Specifically, when a smart contract performed a mload (or other opcodes which access memory) on memory that had been deallocated using ret, it was still able to access the old memory contents. This occurred because the memory region was not zeroed out or otherwise marked as invalid. As a result, smart contracts could potentially read sensitive data left over from other contracts if the same memory was reallocated, violating isolation guarantees between contracts and enabling unintended data leakage.
All users running affected versions of FuelVM that relied on strict memory isolation between smart contracts were impacted.
Patches
The vulnerability was patched by modifying the FuelVM to ensure that memory deallocated with ret was zeroed out or made inaccessible. The fix was included in FuelVM version v0.60.1 and back-ported to v0.59.3. This patch was released to the Fuel network on Friday, April 18th, 2025.
Workarounds
There were no reliable workarounds that fully mitigated the vulnerability. While developers could manually zero out sensitive memory regions before returning from a function, this approach was error-prone and could not be enforced at the VM level. Upgrading to a patched version remained the recommended course of action.
References
- Fix implemented in the FuelVM GitHub repository (https://github.com/FuelLabs/fuel-vm/pull/941)
- Record
GHSA-2pgj-5cv2-6xxw- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N - Weakness
- CWE-416
- Updated
- 2026-11-02
Affected packages
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | GitHub Advisories, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
GHSA-2pgj-5cv2-6xxw is a high vulnerability (CVSS 8.7) in fuel-vm, published October 8, 2025. No source lists public exploit code. Fixed in fuel-vm 0.59.3.