# CVE-2025-64721: Sandboxie's Integer Overflow in SbieIniServer::RC4Crypt allows sandbox escape and SYSTEM compromise

> An integer overflow in Sandboxie allows sandboxed processes to escape isolation and execute arbitrary code with SYSTEM privileges on the host.

- **Severity:** Critical 9.9 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 11 Dec 2025
- **Updated:** 15 Dec 2025
- **Also known as:** GHSA-w476-j57g-96vp

## What is CVE-2025-64721?

CVE-2025-64721 is a critical vulnerability in sandboxie-plus Sandboxie, published on 11 Dec 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Sandboxie is a sandbox-based isolation software for 32-bit and 64-bit Windows NT-based operating systems. In versions 1.16.6 and below, the SYSTEM-level service SbieSvc.exe exposes SbieIniServer::RC4Crypt to sandboxed processes. The handler adds a fixed header size to a caller-controlled value_len without overflow checking. A large value_len (e.g., 0xFFFFFFF0) wraps the allocation size, causing a heap overflow when attacker data is copied into the undersized buffer. This allows sandboxed processes to execute arbitrary code as SYSTEM, fully compromising the host. This issue is fixed in version 1.16.7.

Weakness: CWE-190 (Integer Overflow or Wraparound)

## Which versions are affected by CVE-2025-64721?

It affects 1 product.


Products: Sandboxie-Plus Sandboxie.

## How do I fix CVE-2025-64721?

No fix has been published for CVE-2025-64721 yet. Limit exposure of the affected software until one is available.

## Is CVE-2025-64721 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-64721 exists.

## Other vulnerabilities in sandboxie-plus Sandboxie

- [CVE-2018-18748](https://insights.sbomify.com/CVE-2018-18748/): Security feature bypass in n/a (critical 10.0)
- [CVE-2026-34458](https://insights.sbomify.com/CVE-2026-34458/): Sandboxie-Plus privilege escalation via INI CRLF injection bypassing EditAdminOnly (critical 9.3)
- [CVE-2024-49360](https://insights.sbomify.com/CVE-2024-49360/): Path traversal in Sandboxie (critical 9.2)
- [CVE-2026-34459](https://insights.sbomify.com/CVE-2026-34459/): Sandboxie-Plus sandbox escape via uninitialized memory leak and stack overflow in GetRawInputDeviceInfoSlave (high 8.8)
- [CVE-2026-34464](https://insights.sbomify.com/CVE-2026-34464/): Sandboxie-Plus NamedPipeServer OpenHandler stack overflow via unterminated server field (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-64721 and fix it if it is affected.

What it is: CVE-2025-64721 is a critical vulnerability in sandboxie-plus Sandboxie, published on 11 Dec 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-64721 exists.

Affected product: sandboxie-plus Sandboxie. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-64721/ (Markdown: https://insights.sbomify.com/CVE-2025-64721/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-64721
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-64721
- OSV: https://osv.dev/vulnerability/CVE-2025-64721

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-64721/
Summaries are generated and may contain mistakes; the official description above is the record.