BentoML: SSTI via Unsandboxed Jinja2 in Dockerfile Generation

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2026-35044: 0.40% estimated exploitation activity in the next 30 days; percentile 34.12 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The Dockerfile generation function generatecontainerfile() in src/bentoml/internal/container/generate.py uses an unsandboxed jinja2.Environment with the jinja2.ext.do extension to render user-provided dockerfiletemplate files. When a victim imports a malicious bento archive and runs bentoml containerize, attacker-controlled Jinja2 template code executes arbitrary Python directly on the host machine, bypassing all container isolation. Details The vulnerability exists in the generatecontainerfile() function at src/bentoml/internal/container/generate.py:155-157: This creates an unsandboxed jinja2.Environment with two dangerous extensions: - jinja2.ext.do — enables {% do %} tags that execute arbitrary Python expressions - jinja2.ext.debug — exposes internal template engine state Attack path: 1. Attacker builds a bento with dockerfiletemplate set in bentofile.yaml. During bentoml build, DockerOptions.writetobento() (buildconfig.py:272-276) copies the template file into the bento…

Published by the source

3 Apr 2026, 23:14 UTC

Last modified by the source

8 Jun 2026, 20:15 UTC

Source last checked

26 Oct 2026, 13:45 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-v959-cwq9-7hr6

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-v959-cwq9-7hr6

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# Patch Next advisory brief: CVE-2026-35044

Advisory: BentoML: SSTI via Unsandboxed Jinja2 in Dockerfile Generation
IDs: CVE-2026-35044, GHSA-v959-cwq9-7hr6
Record: https://patchnext.com/advisories/cve-2026-35044 (revision 2, source checked 26 Oct 2026, 13:45 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: bentoml 1.4.38. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI bentoml: affected <= 1.4.37; fixed in 1.4.38

## Suggested inspection (read-only)
- `python -m pip show bentoml`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on bentoml.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-v959-cwq9-7hr6 (OSV record GHSA-v959-cwq9-7hr6 lists affected ranges: PyPI bentoml >=0 <1.4.38 (fixed))
- Verified: https://github.com/advisories/GHSA-v959-cwq9-7hr6 (GitHub-reviewed advisory GHSA-v959-cwq9-7hr6 lists affected ranges: PyPI bentoml >=0 <=1.4.37)

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