Wazuh up to 4.14.3 print_hex_string stack-based overflow

Summaryinfo

A vulnerability classified as critical has been found in Wazuh up to 4.14.3. The impacted element is the function print_hex_string. The manipulation leads to stack-based overflow. This vulnerability is documented as CVE-2026-28221. The attack can be initiated remotely. There is not any exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as critical, has been found in Wazuh up to 4.14.3. This issue affects the function print_hex_string. The manipulation with an unknown input leads to a stack-based overflow vulnerability. Using CWE to declare the problem leads to CWE-121. A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function). Impacted is integrity, and availability. The summary by CVE is:

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.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-28221 since 02/25/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details of the vulnerability are known, but there is no available exploit.

Upgrading to version 4.14.4 eliminates this vulnerability.

The vulnerability is also documented in the databases at EUVD (EUVD-2026-26270) and CERT Bund (WID-SEC-2026-1295). Be aware that VulDB is the high quality source for vulnerability data.

Affected

• Open Source Wazuh

Productinfo

Name

• Wazuh

Version

• 4.14.0
• 4.14.1
• 4.14.2
• 4.14.3

Website

• Product: https://github.com/wazuh/wazuh/

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