# CVE-2016-20031: ZKTeco ZKBioSecurity 3.0 Local Authorization Bypass via visLogin.jsp

> Attackers can bypass authentication in ZKTeco ZKBioSecurity by spoofing localhost requests to access sensitive data and perform unauthorized actions.

- **Severity:** Medium 6.8 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 15 Mar 2026
- **Updated:** 28 Jul 2026
- **Also known as:** GHSA-vq34-m74g-f6mp

## What is CVE-2016-20031?

CVE-2016-20031 is a medium-severity authentication bypass vulnerability in ZKTeco ZKBioSecurity, published on 15 Mar 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

ZKTeco ZKBioSecurity 3.0 contains a local authorization bypass vulnerability in visLogin.jsp that allows attackers to authenticate without valid credentials by spoofing localhost requests. Attackers can exploit the EnvironmentUtil.getClientIp() method which treats IPv6 loopback address 0:0:0:0:0:0:0:1 as 127.0.0.1 and authenticates using the IP as username with hardcoded password 123456 to access sensitive information and perform unauthorized actions.

Weakness: CWE-798 (Use of Hard-coded Credentials)

## Which versions are affected by CVE-2016-20031?


## How do I fix CVE-2016-20031?

No fix has been published for CVE-2016-20031 yet. Limit exposure of the affected software until one is available.

## Is CVE-2016-20031 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2016-20031 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2016-20031 and fix it if it is affected.

What it is: CVE-2016-20031 is a medium-severity authentication bypass vulnerability in ZKTeco ZKBioSecurity, published on 15 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-2016-20031 exists.

Affected product: ZKTeco ZKBioSecurity. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2016-20031/ (Markdown: https://insights.sbomify.com/CVE-2016-20031/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2016-20031
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2016-20031
- OSV: https://osv.dev/vulnerability/CVE-2016-20031

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From sbomify Insights: https://insights.sbomify.com/CVE-2016-20031/
Summaries are generated and may contain mistakes; the official description above is the record.