CVE-2026-48798 is a high-severity (CVSS 7.1) Path Traversal vulnerability in SSH.NET. A fix is available for SSH.NET — see the affected versions and patch details below.
SSH.NET: ScpClient Recursive Download Allows Arbitrary File Write via Server-Controlled SCP Filenames
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-48798.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-48798 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 379,842 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
SSH.NETReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects NuGet packages — download data is not available via public APIs for these ecosystems.
Description
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/authorized_keys, 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 attacker-controlled server.
Remediation
The fixed release ensures that remotely-supplied file and directory names are valid local names such that the constructed local path is contained within the given local directory, and throws ScpException when an invalid name is detected.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| .NETNuGet | SSH.NET | all versions | 2026.0.0dotnet add package SSH.NET --version 2026.0.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for SSH.NET, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update SSH.NET to 2026.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-48798 is resolved across your whole dependency graph.
Workarounds
Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.
Frequently Asked Questions
Is CVE-2026-48798 in your dependencies?
Find it across NuGet, including transitive dependencies.