CVE-2026-41499: Wazuh Buffer Overflow Vulnerability

CVE-2026-41499 Overview

CVE-2026-41499 is a heap-based out-of-bounds write vulnerability affecting the Wazuh security platform, a free and open source solution used for threat prevention, detection, and response. The vulnerability exists in the parse_uname_string() function within remoted_op.c, where multiple instances of a dangerous code pattern fail to validate empty strings before performing write operations.

Critical Impact

Successful exploitation can cause heap corruption leading to denial of service conditions. The vulnerability allows authenticated attackers to write one byte before the allocated buffer, corrupting heap metadata in glibc malloc implementations.

Affected Products

• Wazuh versions 4.0.0 through 4.14.3
• Wazuh Manager/Server components processing agent OS identification data
• Systems using glibc malloc implementation

Discovery Timeline

• 2026-04-29 - CVE CVE-2026-41499 published to NVD
• 2026-04-29 - Last updated in NVD database

Technical Details for CVE-2026-41499

Vulnerability Analysis

This vulnerability is classified as CWE-124 (Buffer Underwrite / Write-what-where Condition). The flaw resides in the parse_uname_string() function which processes OS identification data received from Wazuh agents. The function contains a dangerous code pattern that appears in 4 distinct locations within the same function body.

The core issue involves writing to strlen(ptr) - 1 without first checking whether the string is empty. When processing agent-supplied data, if an empty string is encountered, strlen() returns 0. Since strlen() returns a size_t (an unsigned integer type), subtracting 1 from 0 causes an unsigned integer underflow, wrapping the value to SIZE_MAX.

Due to pointer arithmetic behavior, SIZE_MAX effectively becomes -1, causing the write operation to target exactly 1 byte before the start of the allocated heap buffer. This corrupts heap metadata—specifically the chunk size field used by glibc malloc for memory management—leading to heap corruption.

Root Cause

The root cause is improper input validation combined with unsafe arithmetic on unsigned integers. The function fails to validate that strings are non-empty before performing length-based index calculations. The dangerous pattern ptr[strlen(ptr) - 1] = value assumes the string always contains at least one character. This assumption is violated when processing malformed or empty agent data, triggering the unsigned integer underflow condition.

Attack Vector

The vulnerability is exploitable over the network by authenticated agents communicating with the Wazuh Manager. An attacker with valid agent credentials or the ability to impersonate an agent can send crafted OS identification data containing empty strings in specific fields. When the vulnerable parse_uname_string() function processes this malformed data, the heap corruption occurs, potentially leading to service disruption.

The attack requires network access to the Wazuh Manager's agent communication port and low-level privileges (authenticated agent connection). No user interaction is required for exploitation. The primary impact is availability-related, as heap corruption typically results in application crashes or memory corruption that destabilizes the service.

Detection Methods for CVE-2026-41499

Indicators of Compromise

• Unexpected crashes or restarts of the Wazuh Manager service (wazuh-remoted process)
• Segmentation faults in Wazuh logs associated with the parse_uname_string function
• Heap corruption errors in system logs correlating with agent registration or communication events
• Anomalous agent registration attempts with empty or malformed OS identification strings

Detection Strategies

• Monitor Wazuh Manager process stability and implement alerting on unexpected process terminations
• Implement network traffic analysis for agent-to-manager communications containing anomalously short or empty OS identification fields
• Deploy memory corruption detection tools (AddressSanitizer, Valgrind) in test environments to identify exploitation attempts
• Review Wazuh logs for patterns indicating malformed agent data submissions

Monitoring Recommendations

• Enable verbose logging on Wazuh Manager to capture agent communication details
• Configure process monitoring to alert on wazuh-remoted crashes with heap corruption indicators
• Implement network-level monitoring for unusual patterns in agent registration traffic
• Establish baseline metrics for agent communication patterns to detect anomalies

How to Mitigate CVE-2026-41499

Immediate Actions Required

• Upgrade Wazuh to version 4.14.4 or later immediately to remediate the vulnerability
• Audit active agent connections and verify the legitimacy of all registered agents
• Implement network segmentation to restrict agent communication to trusted network segments
• Review recent Wazuh Manager logs for signs of exploitation attempts or unusual agent behavior

Patch Information

The vulnerability has been patched in Wazuh version 4.14.4. The fix addresses all four instances of the vulnerable code pattern in parse_uname_string() by implementing proper empty string validation before performing length-based calculations. Organizations should upgrade to version 4.14.4 or later as documented in the Wazuh Release v4.14.4. Additional details are available in the GitHub Security Advisory GHSA-qvqj-p8mm-r7h3.

Workarounds

• Restrict network access to Wazuh Manager agent communication ports to only trusted IP addresses or network segments
• Implement strict agent authentication and revoke credentials for any suspicious or unverified agents
• Deploy a web application firewall or network intrusion prevention system to filter malformed agent communications
• Consider temporarily disabling agent registration while implementing the upgrade if immediate patching is not possible

# Restrict agent communication to trusted networks using firewall rules
# Example: Allow only internal network range to communicate with Wazuh Manager
iptables -A INPUT -p tcp --dport 1514 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 1514 -j DROP

# Verify Wazuh version after upgrade
/var/ossec/bin/wazuh-control info | grep "WAZUH_VERSION"