# CVE-2026-26204: Wazuh: Heap-based NULL WRITE Buffer Underflow in GetAlertData

> A heap-based buffer underflow in Wazuh allows attackers to corrupt memory and cause denial of service or potential code execution via crafted alerts.

- **Severity:** Medium 4.4 (`CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 29 Apr 2026
- **Updated:** 30 Apr 2026
- **Also known as:** GHSA-j4c7-hwjw-8857

## What is CVE-2026-26204?

CVE-2026-26204 is a medium-severity memory corruption vulnerability in Wazuh Wazuh, published on 29 Apr 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Wazuh is a free and open source platform used for threat prevention, detection, and response. From version 1.0.0 to before version 4.14.4, a heap-based out-of-bounds WRITE occurs in GetAlertData, resulting in writing a NULL byte exactly 1 byte before the start of the buffer allocated by strdup. Due to unsigned integer underflow and pointer arithmetic wrapping, the write lands at offset -1 from the buffer, corrupting heap metadata. A malicious actor can potentially leverage this issue through a compromised agent to cause denial of service or heap corruption by injecting a specially crafted alert into the alerts log file monitored by wazuh-logcollector. This issue has been patched in version 4.14.4.

Weakness: CWE-191 (Integer Underflow (Wrap or Wraparound)), CWE-124 (Buffer Underwrite)

## Which versions are affected by CVE-2026-26204?

It affects 1 product.


Products: Wazuh Wazuh.

## How do I fix CVE-2026-26204?

No fix has been published for CVE-2026-26204 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-26204 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-26204 exists.

## Other vulnerabilities in Wazuh Wazuh

- [CVE-2025-24016](https://insights.sbomify.com/CVE-2025-24016/): Wazuh Server Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2024-32038](https://insights.sbomify.com/CVE-2024-32038/): Wazuh Analysis Engine Event Decoder Heap-based Buffer Overflow Remote Code Execution Vulnerability (critical 9.8)
- [CVE-2021-44079](https://insights.sbomify.com/CVE-2021-44079/): Command injection in n/a (critical 9.8)
- [CVE-2024-1243](https://insights.sbomify.com/CVE-2024-1243/): Remote code execution and local privilege escalation in Wazuh Windows agent via NetNTLMv2 hash theft (critical 9.5)
- [CVE-2026-61800](https://insights.sbomify.com/CVE-2026-61800/): Wazuh cluster worker file sync allows arbitrary file write under /var/ossec (incomplete fix for CVE-2026-30893) (critical 9.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-26204 and fix it if it is affected.

What it is: CVE-2026-26204 is a medium-severity memory corruption vulnerability in Wazuh Wazuh, published on 29 Apr 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-2026-26204 exists.

Affected product: Wazuh Wazuh. 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-2026-26204/ (Markdown: https://insights.sbomify.com/CVE-2026-26204/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-26204
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-26204
- OSV: https://osv.dev/vulnerability/CVE-2026-26204

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-26204/
Summaries are generated and may contain mistakes; the official description above is the record.