CVE-2026-26204: wazuh Buffer Underflow

Vulnerability summary

CVE-2026-26204 is a medium (CVSS 5.5) Buffer Underflow vulnerability in wazuh. EPSS estimates a 0.18% chance of exploitation in the next 30 days, higher than 7% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 29-04-2026
   PublishedVulnerability first disclosed.
2. 30-04-2026
   Last modifiedVulnerability information updated.

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.

• CWE-124Buffer Underwrite ('Buffer Underflow')The product writes to a buffer using an index or pointer that references a memory location prior to the beginning of the buffer.
• CWE-191Integer Underflow (Wrap or Wraparound)The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result.