# CVE-2016-20030: ZKTeco ZKBioSecurity 3.0 User Enumeration via authLoginAction

> Unauthenticated attackers can enumerate valid usernames in ZKTeco ZKBioSecurity by analyzing responses to login requests, facilitating targeted attacks.

- **Severity:** Critical 9.3 (`CVSS:4.0/AV:N/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:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 15 Mar 2026
- **Updated:** 28 Jul 2026
- **Also known as:** GHSA-5mcw-4937-qq36

## What is CVE-2016-20030?

CVE-2016-20030 is a critical vulnerability in ZKTeco ZKBioSecurity, published on 15 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

ZKTeco ZKBioSecurity 3.0 contains a user enumeration vulnerability that allows unauthenticated attackers to discover valid usernames by submitting partial characters via the username parameter. Attackers can send requests to the authLoginAction!login.do script with varying username inputs to enumerate valid user accounts based on application responses.

Weakness: CWE-551 (Incorrect Behavior Order: Authorization Before Parsing and Canonicalization)

## Which versions are affected by CVE-2016-20030?


## How do I fix CVE-2016-20030?

No fix has been published for CVE-2016-20030 yet. Limit exposure of the affected software until one is available.

## Is CVE-2016-20030 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2016-20030 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2016-20030 and fix it if it is affected.

What it is: CVE-2016-20030 is a critical vulnerability in ZKTeco ZKBioSecurity, published on 15 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2016-20030 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-2016-20030/ (Markdown: https://insights.sbomify.com/CVE-2016-20030/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2016-20030
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2016-20030
- OSV: https://osv.dev/vulnerability/CVE-2016-20030

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From sbomify Insights: https://insights.sbomify.com/CVE-2016-20030/
Summaries are generated and may contain mistakes; the official description above is the record.