{"id":"CVE-2026-28221","summary":"Wazuh: Pre-auth stack-based buffer overflow in wazuh-remoted print_hex_string() due to signed char promotion on x86_64","details":"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 \u003c 0x80). This issue has been patched in version 4.14.4.","aliases":["GHSA-q9vv-7w4c-f4cm"],"modified":"2026-07-08T07:32:28.544667440Z","published":"2026-04-29T17:53:15.374Z","database_specific":{"cwe_ids":["CWE-121","CWE-400"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/28xxx/CVE-2026-28221.json","cna_assigner":"GitHub_M"},"references":[{"type":"WEB","url":"https://github.com/wazuh/wazuh/releases/tag/v4.14.4"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/28xxx/CVE-2026-28221.json"},{"type":"ADVISORY","url":"https://github.com/wazuh/wazuh/security/advisories/GHSA-q9vv-7w4c-f4cm"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-28221"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/wazuh/wazuh","events":[{"introduced":"038fe11d988fa54cca8a6c3101fc7906fad5da3b"},{"fixed":"5933ec9ebee76fb2546e5f7fc9f3a27d0aeca605"}],"database_specific":{"cpe":"cpe:2.3:a:wazuh:wazuh:*:*:*:*:*:*:*:*","source":["AFFECTED_FIELD","CPE_RANGE","REFERENCES"],"extracted_events":[{"introduced":"4.8.0"},{"fixed":"4.14.4"}]}}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-28221.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L"}]}