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

> Attackers can achieve arbitrary file write on the host by exploiting symlink validation flaws in tar extraction, potentially leading to code execution.

- **Severity:** High 8.6 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 3 Mar 2026
- **Updated:** 4 Mar 2026
- **Also known as:** GHSA-m6w7-qv66-g3mf, PYSEC-2026-2398

## What is CVE-2026-27905?

CVE-2026-27905 is a high-severity path traversal vulnerability in BentoML, published on 3 Mar 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official 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.

Weakness: CWE-59 (Improper Link Resolution Before File Access)

## Which versions are affected by CVE-2026-27905?

3 open source packages ship an affected version, including bentoml. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `bentoml` | PyPI | All versions | 1.4.36 |
| `bentoml` | PyPI | All versions | 1.4.36 |
| `bentoml` | PyPI | All versions | 1.4.36 |

Products: Bentoml Bentoml.

## How do I fix CVE-2026-27905?

Upgrade bentoml to 1.4.36 or later.

## Is CVE-2026-27905 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-27905 exists.

## Other vulnerabilities in BentoML

- [CVE-2025-54381](https://insights.sbomify.com/CVE-2025-54381/): BentoML is Vulnerable to an SSRF Attack Through File Upload Processing (critical 9.9)
- [CVE-2025-32375](https://insights.sbomify.com/CVE-2025-32375/): Insecure Deserialization leads to RCE in BentoML's runner server (critical 9.8)
- [CVE-2025-27520](https://insights.sbomify.com/CVE-2025-27520/): BentoML Allows Remote Code Execution (RCE) via Insecure Deserialization (critical 9.8)
- [CVE-2026-44345](https://insights.sbomify.com/CVE-2026-44345/): BentoML: Dockerfile command injection via docker.base_image (high 8.8)
- [CVE-2026-44346](https://insights.sbomify.com/CVE-2026-44346/): BentoML: Dockerfile command injection via envs[*].name in bentofile.yaml (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-27905 and fix it if it is affected.

What it is: CVE-2026-27905 is a high-severity path traversal vulnerability in BentoML, published on 3 Mar 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-27905 exists.

Affected packages and fixed versions:
- bentoml (PyPI): affected all versions; fixed in 1.4.36
- bentoml (PyPI): affected all versions; fixed in 1.4.36
- bentoml (PyPI): affected all versions; fixed in 1.4.36

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-27905/ (Markdown: https://insights.sbomify.com/CVE-2026-27905/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-27905
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-27905
- OSV: https://osv.dev/vulnerability/CVE-2026-27905

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-27905/
Summaries are generated and may contain mistakes; the official description above is the record.