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

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-03-03 · updated 2026-10-07
Weakness: CWE-59

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.

Affected products

BentoML: before 1.4.36 — fixed in 1.4.36

How to fix

Upgrade to a fixed version: BentoML 1.4.36. Check the vendor advisory for mitigations.

References

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