From e02ae6b2fb69668d1cd7d07cb873dfcdd9cf1e42 Mon Sep 17 00:00:00 2001
From: andres-portainer <91705312+andres-portainer@users.noreply.github.com>
Date: Mon, 16 Feb 2026 11:26:51 -0300
Subject: [PATCH] fix(archive): prevent file traversal vulnerability BE-12582
 (#1875)

---
 api/archive/targz.go      |  3 ++-
 api/archive/targz_test.go | 56 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+), 1 deletion(-)

diff --git a/api/archive/targz.go b/api/archive/targz.go
index e5167d18c..2f3496329 100644
--- a/api/archive/targz.go
+++ b/api/archive/targz.go
@@ -10,6 +10,7 @@ import (
 	"path/filepath"
 	"strings"
 
+	"github.com/portainer/portainer/api/filesystem"
 	"github.com/portainer/portainer/api/logs"
 )
 
@@ -108,7 +109,7 @@ func ExtractTarGz(r io.Reader, outputDirPath string) error {
 		case tar.TypeDir:
 			// skip, dir will be created with a file
 		case tar.TypeReg:
-			p := filepath.Clean(filepath.Join(outputDirPath, header.Name))
+			p := filesystem.JoinPaths(outputDirPath, header.Name)
 			if err := os.MkdirAll(filepath.Dir(p), 0o744); err != nil {
 				return fmt.Errorf("Failed to extract dir %s", filepath.Dir(p))
 			}
diff --git a/api/archive/targz_test.go b/api/archive/targz_test.go
index a06312a6b..28598b208 100644
--- a/api/archive/targz_test.go
+++ b/api/archive/targz_test.go
@@ -1,12 +1,15 @@
 package archive
 
 import (
+	"archive/tar"
+	"compress/gzip"
 	"os"
 	"os/exec"
 	"path"
 	"path/filepath"
 	"testing"
 
+	"github.com/portainer/portainer/api/filesystem"
 	"github.com/rs/zerolog/log"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -108,3 +111,56 @@ func Test_shouldCreateArchive2(t *testing.T) {
 	wasExtracted("dir/inner")
 	wasExtracted("dir/.dotfile")
 }
+
+func TestExtractTarGzPathTraversal(t *testing.T) {
+	testDir := t.TempDir()
+
+	// Create an evil file with a path traversal attempt
+	tarPath := filesystem.JoinPaths(testDir, "evil.tar.gz")
+
+	evilFile, err := os.Create(tarPath)
+	require.NoError(t, err)
+
+	gzWriter := gzip.NewWriter(evilFile)
+	tarWriter := tar.NewWriter(gzWriter)
+
+	content := []byte("evil content")
+
+	header := &tar.Header{
+		Name:     "../evil.txt",
+		Mode:     0600,
+		Size:     int64(len(content)),
+		Typeflag: tar.TypeReg,
+	}
+
+	err = tarWriter.WriteHeader(header)
+	require.NoError(t, err)
+
+	_, err = tarWriter.Write(content)
+	require.NoError(t, err)
+
+	err = tarWriter.Close()
+	require.NoError(t, err)
+
+	err = gzWriter.Close()
+	require.NoError(t, err)
+
+	err = evilFile.Close()
+	require.NoError(t, err)
+
+	// Attempt to extract the evil file
+	extractionDir := filesystem.JoinPaths(testDir, "extraction")
+	err = os.Mkdir(extractionDir, 0700)
+	require.NoError(t, err)
+
+	tarFile, err := os.Open(tarPath)
+	require.NoError(t, err)
+
+	// Check that the file didn't escape
+	err = ExtractTarGz(tarFile, extractionDir)
+	require.NoError(t, err)
+	require.NoFileExists(t, filesystem.JoinPaths(testDir, "evil.txt"))
+
+	err = tarFile.Close()
+	require.NoError(t, err)
+}