Multiple Vulnerabilities in Apache HTTP Server Allow Remote Code Execution, Privilege Escalation, and Denial of Service

On May 5, 2026, ANSSI published an advisory regarding multiple vulnerabilities affecting Apache HTTP Server versions prior to 2.4.67. These vulnerabilities, detailed in the Apache HTTP Server CHANGES_2.4.67 security bulletin released on May 4, 2026, pose significant risks, including the potential for remote code execution, privilege escalation, and denial-of-service attacks. Successful exploitation of these vulnerabilities could allow attackers to gain unauthorized access to systems, compromise sensitive data, and disrupt critical services. Given the widespread use of Apache HTTP Server, these vulnerabilities represent a critical threat requiring immediate attention and patching. The vulnerabilities are tracked as CVE-2026-23918, CVE-2026-24072, CVE-2026-28780, CVE-2026-29168, CVE-2026-29169, CVE-2026-33006, CVE-2026-33007, CVE-2026-33523, CVE-2026-33857, CVE-2026-34032, and CVE-2026-34059.

Attack Chain

The advisory does not specify the exact attack chain; however, based on the nature of the vulnerabilities (RCE, privilege escalation, and DoS), the following generic attack chain is likely:

1. Initial Access: An attacker identifies a vulnerable Apache HTTP Server instance running a version prior to 2.4.67.
2. Vulnerability Exploitation: The attacker crafts a malicious request targeting one of the disclosed vulnerabilities (e.g., CVE-2026-23918).
3. Code Execution: Successful exploitation results in the execution of arbitrary code on the server.
4. Privilege Escalation: If the initial code execution occurs with limited privileges, the attacker may exploit a separate vulnerability (e.g., CVE-2026-24072) to escalate privileges to a higher level, such as root or SYSTEM.
5. Persistence (Optional): The attacker may establish persistence by installing a backdoor or modifying system configurations.
6. Lateral Movement (Optional): With elevated privileges, the attacker may attempt to move laterally to other systems within the network.
7. Data Exfiltration / System Damage: Depending on their objectives, the attacker may exfiltrate sensitive data or cause damage to the system, potentially leading to a denial of service (e.g., through CVE-2026-28780).
8. Denial of Service: Alternatively, the attacker directly exploits a DoS vulnerability to disrupt the availability of the service.

Impact

Successful exploitation of these vulnerabilities can lead to severe consequences. An attacker could gain complete control of the affected server, leading to data breaches, system compromise, and service disruption. The advisory does not specify the number of victims or sectors targeted, but given the widespread deployment of Apache HTTP Server, the potential impact is significant. Organizations relying on Apache HTTP Server for critical services could experience substantial financial and reputational damage.

Recommendation

• Apply the security patches provided by Apache to upgrade to version 2.4.67 or later to address the vulnerabilities described in the Apache HTTP Server CHANGES_2.4.67 bulletin.
• Monitor web server logs for suspicious activity and exploit attempts targeting the listed CVEs, using a web application firewall (WAF) or intrusion detection system (IDS).
• Deploy the provided Sigma rules to your SIEM to detect potential exploitation attempts. Enable webserver logging to activate these rules.
• Review and harden Apache HTTP Server configurations according to security best practices to minimize the attack surface.
• Prioritize patching internet-facing Apache HTTP Server instances to reduce the risk of remote exploitation.