# CVE-2026-34596: Sandboxie-Plus local privilege escalation via TOCTOU race condition in UpdUtil addon installation

> An attacker can exploit a race condition during addon installation to execute arbitrary code with SYSTEM privileges on Windows.

- **Severity:** Medium 5.4 (`CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 5 May 2026
- **Updated:** 7 May 2026
- **Also known as:** GHSA-xjvp-63f2-v585

## What is CVE-2026-34596?

CVE-2026-34596 is a medium-severity vulnerability in sandboxie-plus Sandboxie, published on 5 May 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

Sandboxie-Plus is an open source sandbox-based isolation software for Windows. In versions 1.17.2 and earlier, a Time-of-Check-to-Time-of-Use (TOCTOU) race condition exists during addon installation. When a user installs an addon through the SandMan interface, UpdUtil.exe is spawned as SYSTEM by SbieSvc but stages files in the user-writable %TEMP%\sandboxie-updater directory. After UpdUtil verifies file hashes against the signed addon manifest, install.bat extracts files.cab and executes config.exe from its contents. Between hash verification and extraction, an unprivileged user can replace files.cab with a crafted cabinet containing a malicious executable, which is then run as SYSTEM. No UAC prompt is required.

This issue has been fixed in version 1.17.3.

Weakness: CWE-367 (Time-of-check Time-of-use (TOCTOU) Race Condition)

## Which versions are affected by CVE-2026-34596?

It affects 1 product.


Products: Sandboxie-Plus Sandboxie.

## How do I fix CVE-2026-34596?

No fix has been published for CVE-2026-34596 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-34596 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-34596 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-2025-64721](https://insights.sbomify.com/CVE-2025-64721/): Sandboxie's Integer Overflow in SbieIniServer::RC4Crypt allows sandbox escape and SYSTEM compromise (critical 9.9)
- [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)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-34596 and fix it if it is affected.

What it is: CVE-2026-34596 is a medium-severity vulnerability in sandboxie-plus Sandboxie, published on 5 May 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-34596 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-2026-34596/ (Markdown: https://insights.sbomify.com/CVE-2026-34596/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-34596
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-34596
- OSV: https://osv.dev/vulnerability/CVE-2026-34596

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-34596/
Summaries are generated and may contain mistakes; the official description above is the record.