CVE-2026-46729
Description
A flaw was found in the mod_heartmonitor module of the Apache HTTP Server. A remote, unauthenticated attacker can exploit a NULL pointer dereference vulnerability when the module is configured with a unicast listener. By sending specially crafted network traffic to the listening service, an attacker can crash the server process, resulting in a Denial of Service (DoS).
Mitigation
Disable the mod_heartmonitor module or restrict network access to the monitoring port:
1. Disable the module:
Comment out the LoadModule directive for mod_heartmonitor in the Apache configuration (typically located in `/etc/httpd/conf.modules.d/00-base.conf` or a custom configuration file):
# LoadModule heartmonitor_module modules/mod_heartmonitor.so
Then reload the web server configuration:
systemctl reload httpd
2. Restrict network reachability:
If mod_heartmonitor is required, configure firewall rules using firewalld to permit traffic to the HeartbeatListen unicast port only from authorized backend nodes:
firewall-cmd --permanent --zone=trusted --add-source=<TRUSTED_IP_RANGE>
firewall-cmd --reload
Caveat: Disabling mod_heartmonitor prevents mod_lbmethod_heartbeat from receiving backend node status, which disables heartbeat-based dynamic load balancing.
Warning: Modifying Apache configuration files requires reloading or restarting httpd, which may briefly interrupt active network connections.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.5 | N/A | 7.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
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