goshs has a Path Traversal issue

## 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.

Source published

28 Jul 2026 22:08:53 UTC

Source modified

18 Aug 2026 15:10:58 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

Publisher rating · MODERATE