CVE-2026-112339 in Wazuh
Summary
by MITRE • 11/06/2026
Wazuh from 3.9.0 before 4.14.9 contains a missing TLS hostname verification vulnerability in the fluent-forward module's wm_fluent_ssl_ctx() that allows network attackers to impersonate the Fluentd collector by presenting any certificate chaining to the configured ca_file. Attackers who redirect the connection via DNS, ARP, or on-path positions can receive forwarded security telemetry and the shared_key_hexdigest for offline cracking.
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Analysis
by VulDB Data Team • 11/06/2026
The vulnerability identified in Wazuh versions ranging from 3.9.0 up to but not including 4.14.9 represents a critical failure in transport layer security implementation within the fluent-forward module. Specifically, the flaw resides in the wm_fluent_ssl_ctx function which is responsible for establishing secure communication channels with Fluentd collectors. The core technical deficiency is the absence of TLS hostname verification during the certificate validation process. In standard Secure Sockets Layer and Transport Layer Security protocols, it is mandatory not only to verify that a server's certificate is signed by a trusted Certificate Authority but also to ensure that the identity presented in the certificate matches the intended destination host. By omitting this check, the Wazuh agent fails to confirm whether the remote Fluentd collector is genuinely the entity it claims to be, thereby breaking the chain of trust essential for secure data transmission.
This architectural oversight allows network attackers to perform man-in-the-middle attacks with relative ease when they possess the ability to intercept or redirect traffic. If an attacker can manipulate DNS responses, exploit ARP spoofing vulnerabilities on a local area network, or position themselves as an active intermediary in the communication path, they can present any valid certificate chain that chains back to the configured Certificate Authority file without triggering a security alert from the Wazuh agent. The agent will accept this fraudulent connection because it only validates the signature of the CA and ignores the subject alternative names or common name fields within the server certificate. Consequently, the encrypted tunnel is established with an adversary rather than the legitimate log aggregation service, effectively neutralizing the confidentiality guarantees provided by TLS encryption for data in transit.
The operational impact of this vulnerability is severe due to the sensitive nature of the data being transmitted through these channels. Wazuh agents are responsible for collecting and forwarding security telemetry, which includes system logs, file integrity monitoring results, and potentially authentication events. Furthermore, the configuration often involves shared keys used for agent-authentication mechanisms. When an attacker successfully impersonates the Fluentd collector using this flaw, they gain access to a continuous stream of forwarded security telemetry data. More critically, the attacker can capture the shared_key_hexdigest which is transmitted during certain handshake or re-authentication phases. This digest serves as a credential component that can be extracted and subjected to offline brute-force attacks. Given sufficient computational resources, an adversary could reverse-engineer these digests to obtain valid authentication credentials for other agents within the environment, leading to widespread compromise of the monitoring infrastructure.
From a classification perspective, this vulnerability aligns with CWE-295 Improper Certificate Validation, specifically the sub-category related to missing hostname verification. It also maps directly to MITRE ATT&CK technique T1078 Valid Accounts and potentially T1046 Network Service Discovery if used for further reconnaissance, but most accurately reflects aspects of Man-in-the-Middle attacks such as those described in techniques involving SSL stripping or certificate spoofing where the victim's trust model is bypassed. The exploitation requires network-level access to redirect traffic, meaning it poses a higher risk on untrusted networks like public Wi-Fi compared to isolated internal segments, although ARP poisoning remains a viable threat vector within compromised local subnets regardless of physical isolation efforts that do not include switch port security or dynamic ARP inspection.
Mitigation for this vulnerability is primarily achieved through upgrading the Wazuh installation to version 4.14.9 or later where the hostname verification logic has been corrected in the wm_fluent_ssl_ctx function. Organizations running affected versions should prioritize patching immediately, especially if agents are deployed on networks that cannot be fully trusted or segmented from potential attacker-controlled segments. In addition to software updates, administrators should enforce strict network segmentation policies and implement dynamic ARP inspection on switches where possible to mitigate the risk of traffic redirection via ARP spoofing. Furthermore, monitoring for unusual certificate presentations during TLS handshakes can help detect exploitation attempts in real-time before significant data exfiltration occurs. It is also advisable to rotate any shared keys that may have been exposed if an incident response investigation confirms compromise through this vector.