medium

CVE-2026-66063

Go · goshs.de/goshs/v2

Summary

goshs has a Path Traversal issue

Severity
medium
CVSS
6.5
EPSS
0.3% (p28)
CWE
CWE-22
Also known as
GHSA-wg2q-39h6-66x9#goshs.de/goshs/v2
Published
2026-07-28
Updated
2026-07-28

Advisory details

Summary

The multipart upload filename fix splits on the path separator but never rejects dot-dot, allowing a write outside the served tree.

Finding (Medium): upload filename escapes the served tree (residual of CVE-2026-35393)

The multipart filename fix (updown.go lines 135-136) splits on the path separator but never rejects "..". Uploading with filename=".." results in os.Create against the parent of the upload folder with a trailing marker character, outside the served tree, and the subsequent failed rename leaves that file behind. Verified: a file containing ESCAPED_WRITE_PROOF was written outside the webroot, unauthenticated, with the default configuration. Not claimed: a Windows-specific variant (Go's Part.FileName() already applies filepath.Base).

Suggested fixes

  1. Reject any upload filename that is "..", is empty after sanitisation, or resolves outside the upload folder; validate the final resolved destination rather than only transforming the input.

Tooling

AI assistance was used while investigating. The finding was reproduced against a running server on loopback.

References

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Sources: CISA KEV (public domain), OSV.dev & GitHub Advisory Database (CC-BY-4.0), FIRST EPSS, NVD/CWE (public domain). Served live from the Stateward advisory database.