CVE-2026-8756 — HIGH (CVSS 7.3)

CISO Take

CVE-2026-8756 is an unauthenticated path traversal in the Gradio preprocessing interface of fishaudio Bert-VITS2, a widely-used open-source voice synthesis model toolkit. The `generate_config` function accepts user-controlled `data_dir` input without sanitization, allowing remote attackers to traverse outside the intended working directory and read or write arbitrary files on the host. While EPSS data is not yet available and the vulnerability is absent from CISA KEV, the CVSS 7.3 HIGH score reflects no authentication required, no user interaction, and trivial network-accessible exploitation — a public proof-of-concept exploit has already been disclosed on GitHub, meaning the window before widespread scanning begins is short. Teams running Bert-VITS2 training or preprocessing pipelines should immediately restrict the Gradio interface to localhost-only binding (`server_name='127.0.0.1'`) and audit whether any instance is currently exposed on internal or external networks.

Sources: NVD ATLAS GitHub Advisory

What is the risk?

HIGH operational risk for ML engineering teams running Bert-VITS2 preprocessing pipelines. No authentication bypass needed — the Gradio interface accepts unauthenticated requests by default when server binding is not restricted. Combining network-accessible path traversal (CVSS AV:N/AC:L/PR:N/UI:N) with a live public PoC yields a near-certain exploitation scenario for any exposed instance. Training environments often store API keys, SSH keys, and cloud storage credentials in nearby configuration files, elevating the blast radius beyond the ML artifact scope. The absence of versioning in this project means no patched release exists; mitigations are configuration-only.

Attack Kill Chain

Discovery

Attacker scans the internet or internal network for Gradio interfaces on default port 7860 and identifies an exposed Bert-VITS2 preprocessing endpoint with no authentication.

AML.T0006

Exploitation

Using the public GitHub PoC, attacker submits a crafted request to the `generate_config` Gradio function with path traversal sequences in the `data_dir` argument, bypassing directory restrictions.

AML.T0049

Collection

Attacker reads arbitrary files from the host filesystem reachable by the process user — targeting `.env` files, Hugging Face tokens, SSH keys, and training dataset manifests.

AML.T0037

Exfiltration

Harvested credentials and AI artifacts are returned directly via HTTP responses from the Gradio interface, enabling follow-on access to model registries, cloud storage buckets, or compute infrastructure.

AML.T0025

Discovery

Attacker scans the internet or internal network for Gradio interfaces on default port 7860 and identifies an exposed Bert-VITS2 preprocessing endpoint with no authentication.

AML.T0006

Exploitation

Using the public GitHub PoC, attacker submits a crafted request to the `generate_config` Gradio function with path traversal sequences in the `data_dir` argument, bypassing directory restrictions.

AML.T0049

Collection

Attacker reads arbitrary files from the host filesystem reachable by the process user — targeting `.env` files, Hugging Face tokens, SSH keys, and training dataset manifests.

AML.T0037

Exfiltration

Harvested credentials and AI artifacts are returned directly via HTTP responses from the Gradio interface, enabling follow-on access to model registries, cloud storage buckets, or compute infrastructure.

AML.T0025

Severity & Risk

CVSS 3.1

7.3 / 10

EPSS

0.1%

chance of exploitation in 30 days

Higher than 25% of all CVEs

Source: EPSS v3 — FIRST.org

Exploitation Status

No known exploitation

Sophistication

Trivial

Attack Surface

AV Network

AC Low

PR None

UI None

S Unchanged

C Low

I Low

A Low

What should I do?

6 steps

Immediately bind the Gradio interface to localhost: add server_name='127.0.0.1' to any gr.Blocks().launch() call in webui_preprocess.py.
Since the project has no versioning, pin to a commit after the vendor addresses this — track the repository for a fix commit post-disclosure.
Audit all running Bert-VITS2 instances using ss -tlnp | grep 7860 (default Gradio port) to identify exposed services.
Apply network-level controls: block inbound access to Gradio default ports (7860-7870) at the firewall or security group level.
For detection, monitor file access logs for path traversal patterns (../) in web server request logs or using auditd rules on sensitive directories.
Rotate any credentials stored in files accessible from the Bert-VITS2 working directory.

Classification

Data Extraction Code Execution Framework Training Data AML.T0025 - Exfiltration via Cyber Means AML.T0035 - AI Artifact Collection AML.T0037 - Data from Local System AML.T0049 - Exploit Public-Facing Application

Compliance Impact

This CVE is relevant to:

EU AI Act

Article 15 - Accuracy, robustness and cybersecurity

ISO 42001

A.6.2.6 - Security of AI systems

NIST AI RMF

MANAGE 2.2 - Mechanisms are in place and applied to sustain the value of deployed AI systems

OWASP LLM Top 10

LLM06:2023 - Sensitive Information Disclosure

Frequently Asked Questions

What is CVE-2026-8756?

CVE-2026-8756 is an unauthenticated path traversal in the Gradio preprocessing interface of fishaudio Bert-VITS2, a widely-used open-source voice synthesis model toolkit. The `generate_config` function accepts user-controlled `data_dir` input without sanitization, allowing remote attackers to traverse outside the intended working directory and read or write arbitrary files on the host. While EPSS data is not yet available and the vulnerability is absent from CISA KEV, the CVSS 7.3 HIGH score reflects no authentication required, no user interaction, and trivial network-accessible exploitation — a public proof-of-concept exploit has already been disclosed on GitHub, meaning the window before widespread scanning begins is short. Teams running Bert-VITS2 training or preprocessing pipelines should immediately restrict the Gradio interface to localhost-only binding (`server_name='127.0.0.1'`) and audit whether any instance is currently exposed on internal or external networks.

Is CVE-2026-8756 actively exploited?

No confirmed active exploitation of CVE-2026-8756 has been reported, but organizations should still patch proactively.

How to fix CVE-2026-8756?

1. Immediately bind the Gradio interface to localhost: add `server_name='127.0.0.1'` to any `gr.Blocks().launch()` call in `webui_preprocess.py`. 2. Since the project has no versioning, pin to a commit after the vendor addresses this — track the repository for a fix commit post-disclosure. 3. Audit all running Bert-VITS2 instances using `ss -tlnp | grep 7860` (default Gradio port) to identify exposed services. 4. Apply network-level controls: block inbound access to Gradio default ports (7860-7870) at the firewall or security group level. 5. For detection, monitor file access logs for path traversal patterns (`../`) in web server request logs or using auditd rules on sensitive directories. 6. Rotate any credentials stored in files accessible from the Bert-VITS2 working directory.

What systems are affected by CVE-2026-8756?

This vulnerability affects the following AI/ML architecture patterns: training pipelines, ml ui interfaces, model serving.

What is the CVSS score for CVE-2026-8756?

CVE-2026-8756 has a CVSS v3.1 base score of 7.3 (HIGH). The EPSS exploitation probability is 0.09%.

Technical Details

NVD Description

A vulnerability has been found in fishaudio Bert-VITS2 up to 8f7fbd8c4770965225d258db548da27dc8dd934c. The impacted element is the function generate_config of the file webui_preprocess.py of the component Gradio Interface. Such manipulation of the argument data_dir leads to path traversal. The attack can be launched remotely. The exploit has been disclosed to the public and may be used. This product does not use versioning. This is why information about affected and unaffected releases are unavailable. The vendor was contacted early about this disclosure but did not respond in any way.

Exploitation Scenario

An attacker scans for internet-exposed services on port 7860 (Gradio default) and identifies a Bert-VITS2 preprocessing instance with no authentication. Using the public GitHub PoC, they submit a crafted POST request to the `generate_config` Gradio endpoint with `data_dir` set to a path traversal sequence such as `../../../../../../home/user/.ssh/` or `../../opt/ml/.env`. The server processes the traversal without validation and returns file contents or writes a malicious config. The attacker exfiltrates Hugging Face API tokens, cloud storage credentials, or SSH private keys found in adjacent directories — enabling persistent access to model registries, training data buckets, or the underlying compute infrastructure.