GHSA-Q939-RPR3-3284
Vulnerability from github – Published: 2026-08-12 15:19 – Updated: 2026-08-18 18:05Summary
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": [
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 2025.1.0"
},
"package": {
"ecosystem": "NuGet",
"name": "SSH.NET"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "2026.0.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-48798"
],
"database_specific": {
"cwe_ids": [
"CWE-22",
"CWE-73"
],
"github_reviewed": true,
"github_reviewed_at": "2026-08-12T15:19:10Z",
"nvd_published_at": "2026-08-18T15:16:54Z",
"severity": "HIGH"
},
"details": "## Summary\n\n`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](https://github.com/advisories/GHSA-jr78-hfw4-xp7g), but with directory traversal capability.\n\n## Impact\n\nA 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.\n\n## Remediation\n\nThe 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.\n\n[600be0de543765995a189b5d7cd4efac5007f3ce](https://github.com/sshnet/SSH.NET/commit/600be0de543765995a189b5d7cd4efac5007f3ce)",
"id": "GHSA-q939-rpr3-3284",
"modified": "2026-08-18T18:05:07Z",
"published": "2026-08-12T15:19:10Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/sshnet/SSH.NET/security/advisories/GHSA-q939-rpr3-3284"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-48798"
},
{
"type": "WEB",
"url": "https://github.com/sshnet/SSH.NET/commit/600be0de543765995a189b5d7cd4efac5007f3ce"
},
{
"type": "PACKAGE",
"url": "https://github.com/sshnet/SSH.NET"
},
{
"type": "WEB",
"url": "https://github.com/sshnet/SSH.NET/releases/tag/2026.0.0"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L",
"type": "CVSS_V3"
}
],
"summary": "SSH.NET: ScpClient Recursive Download Allows Arbitrary File Write via Server-Controlled SCP Filenames"
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.