# CVE-2026-59786: Active agent heartbeat missing TLS check

> Attackers can bypass TLS authentication to report arbitrary hosts as available, compromising data integrity in Zabbix Server and Proxy.

- **Severity:** Medium 6.9 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/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:** Yes
- **Published:** 5 Oct 2026
- **Updated:** 5 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-59786, GHSA-jmxh-h64m-45qp, UBUNTU-CVE-2026-59786

## What is CVE-2026-59786?

CVE-2026-59786 is a medium-severity missing authorization vulnerability in Zabbix, published on 5 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Zabbix Server and Proxy accept the active agent heartbeat message regardless of the configured PSK or certificate authentication. This means someone with access to the Zabbix trapper port can report an arbitrary host using an active agent as available, resulting in a loss of integrity.

Weakness: CWE-940 (Improper Verification of Source of a Communication Channel)

## Which versions are affected by CVE-2026-59786?


## How do I fix CVE-2026-59786?

Apply the vendor's patch.

## Is CVE-2026-59786 being exploited?

There is no known exploitation of CVE-2026-59786 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-59786 and fix it if it is affected.

What it is: CVE-2026-59786 is a medium-severity missing authorization vulnerability in Zabbix, published on 5 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-59786 in the wild and no public exploit code.

Affected product: Zabbix. 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-2026-59786/ (Markdown: https://insights.sbomify.com/CVE-2026-59786/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-59786
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-59786
- OSV: https://osv.dev/vulnerability/CVE-2026-59786

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-59786/
Summaries are generated and may contain mistakes; the official description above is the record.