CVE-2025-64721 is a critical (CVSS 10.0) integer overflow in Sandboxie, the Windows sandboxing tool. A process inside a sandbox can corrupt memory in the SYSTEM service SbieSvc.exe and escape to the host. The record names versions 1.16.6 and below. Version 1.16.7 fixes it, so update now.
What's affected
The record says Sandboxie versions 1.16.6 and below are affected, and that the fix shipped in 1.16.7. The GitHub advisory is a little more specific about the start of the range. It lists affected versions as 1.14.0 and later, with 1.16.7 as the patched version. If you run a build older than 1.14.0, the advisory does not list it, so confirm with the project before you assume it is safe.
The flaw lives in SbieSvc.exe, the SYSTEM level service that Sandboxie runs on the host. A handler named SbieIniServer::RC4Crypt is reachable from processes running inside a sandbox. That reach is the whole point of the issue, because sandboxed code is supposed to be untrusted.
Severity is consistent across the sources. The record gives a CVSS 3.1 score of 10.0 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H) and the advisory marks it Critical. One nuance matters for planning. The advisory says causing a crash is trivial, while reliable code execution as SYSTEM needs complex exploitation techniques. The record, by contrast, says the weakness allows arbitrary code execution as SYSTEM. Treat the worst case as real.
How to check if you're exposed
Check the installed version first. In the Sandboxie Plus window, open the Help menu and choose About. You can also read the file version of the service binary from PowerShell. Adjust the path if you installed to a different folder:
(Get-Item "C:\Program Files\Sandboxie-Plus\SbieSvc.exe").VersionInfo.FileVersion
On a fleet, ask your software inventory or endpoint management tool for the Sandboxie and Sandboxie Plus package version. Anything below 1.16.7 should be queued for update.
Then think about how you use it. If you only run trusted software in Sandboxie, the exposure is lower than if you use it to open unknown downloads or suspicious attachments. The second case is exactly where an escape matters.
What to do now
- Update Sandboxie Plus to 1.16.7 or later from the project's release page.
- Restart the Sandboxie service or reboot so the old SbieSvc.exe is no longer running.
- Until you have updated, stop using sandboxes to open untrusted files on affected machines.
- Add Sandboxie to your software inventory if it is missing. Sandbox tools are easy to forget because they are installed by individuals.
- If a machine ran untrusted code in a sandbox on an affected version, review it as you would any machine that may have been exposed to local privilege escalation.
Why it matters
The cause is an integer overflow (CWE-190). The handler adds a fixed header size to a length value that the caller controls, and it does not check whether the addition wraps around. With a very large length, the sum wraps to a small number, a small buffer is allocated, and the later copy writes past the end of it. That is a heap overflow in a service that runs as SYSTEM.
A sandbox is a promise that code inside cannot affect the host. When a privileged helper service accepts input from inside the sandbox, every parser in that service becomes part of the security boundary. One missing overflow check turns the boundary into a door. The record does not flag this CVE as exploited in the wild, and it is not in the CISA catalog. A critical score and a public advisory are still enough reason to patch promptly. The free Safeguard dependency scan can list the packages in a project and flag known CVEs, and the Gold directory keeps a page for each one.
Try it yourself
Click through it at your own pace, or open it full screen.
Quick check
Does the fix need anything besides the update?
The advisory lists 1.16.7 as the patched version and names no extra configuration step. Restart the service or the machine after updating so the fixed service binary is the one running.
Is CVE-2025-64721 exploited in the wild?
Neither the record nor the advisory says so, and the record's KEV flag is false. The advisory does include a proof of concept that crashes the service, so the weakness is well understood.
Sources
Last reviewed: 18 October 2026.
