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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.1 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L

EPSS

• CVE-2026-48798: 0.42% estimated exploitation activity in the next 30 days; percentile 36.47 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary ScpClient.Download(string directoryName, DirectoryInfo directoryInfo) writes files and directories using names returned by the remote SCP server during recursive downloads, with no validation that the resulting path stays inside the requested local directory. A malicious, compromised, or man-in-the-middle SCP server can return names containing ../ sequences (or absolute paths), causing the client to create directories and write/overwrite files anywhere the client process has access. This is similar to OpenSSH CVE-2019-6111, but with directory traversal capability. Impact A malicious/compromised/MITM SCP server can create or write files outside the intended download directory, anywhere the client process can write. Overwriting files such as ~/.ssh/authorizedkeys, shell rc files, cron entries, or application binaries/config can lead to persistence, privilege escalation, or remote code execution on the client host. Requires the victim to perform a directory download from the…

Published by the source

12 Aug 2026, 15:19 UTC

Last modified by the source

18 Aug 2026, 18:15 UTC

Source last checked

26 Oct 2026, 17:05 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-q939-rpr3-3284

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-q939-rpr3-3284

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# Patch Next advisory brief: CVE-2026-48798

Advisory: SSH.NET: ScpClient Recursive Download Allows Arbitrary File Write via Server-Controlled SCP Filenames
IDs: CVE-2026-48798, GHSA-q939-rpr3-3284
Record: https://patchnext.com/advisories/cve-2026-48798 (revision 2, source checked 26 Oct 2026, 17:05 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: ssh.net 2026.0.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- NuGet ssh.net: affected <= 2025.1.0; fixed in 2026.0.0

## Suggested inspection (read-only)
- NuGet ssh.net: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on ssh.net.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-q939-rpr3-3284 (OSV record GHSA-q939-rpr3-3284 lists affected ranges: NuGet ssh.net >=0 <2026.0.0 (fixed))
- Verified: https://github.com/advisories/GHSA-q939-rpr3-3284 (GitHub-reviewed advisory GHSA-q939-rpr3-3284 lists affected ranges: NuGet ssh.net >=0 <=2025.1.0)

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