# CVE-2026-28221

> Vulnerability · severity: **MEDIUM** (CVSS 6.5).

## Description

Wazuh is a free and open source platform used for threat prevention, detection, and response. From version 4.8.0 to before version 4.14.4, a stack-based buffer overflow exists in print_hex_string() in wazuh-remoted. The bug is triggered when formatting attacker-controlled bytes using sprintf(dst_buf + 2*i, "%.2x", src_buf[i]) on platforms where char is treated as signed and the compiled code sign-extends bytes before the variadic call. For input bytes such as 0xFF, the formatting can emit "ffffffff" (8 chars) instead of "ff" (2 chars), causing an out-of-bounds write past a fixed 2049-byte stack buffer. The vulnerable path is reachable remotely prior to any agent authentication/registration logic via TCP/1514 when an oversized length prefix causes the “unexpected message (hex)” diagnostic path to run. Additionally, the same unauthenticated oversized-message diagnostic path logs an attacker-controlled hex dump to /var/ossec/logs/ossec.log for each trigger, allowing remote log amplification that can degrade monitoring fidelity and consume disk/I/O. This log amplification is reachable even without triggering the sign-extension overflow (e.g., using bytes < 0x80). This issue has been patched in version 4.14.4.

## Key facts

- **CVE ID:** CVE-2026-28221
- **Published:** 2026-04-29
- **CVSS severity:** MEDIUM
- **CVSS base score:** 6.5
- **CWE codes:** CWE-121, CWE-400

## Affected products

- `wazuh:wazuh`

## Primary sources

- NIST NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-28221

## Citation

> AI Analytics. CVE-2026-28221. Retrieved 2026-07-13 from https://api.ai-analytics.org/cve/CVE-2026-28221. Derived from NIST NVD. Licensed CC0.

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