Dnsmasq Vulnerability Allows Remote DoS via Crafted BOOTREPLY
The National Vulnerability Database has identified CVE-2026-6507, a critical flaw in the widely used dnsmasq network utility. Attackers can trigger an out-of-bounds write by sending a malicious BOOTREPLY packet to a dnsmasq server specifically configured with the --dhcp-split-relay option. This vulnerability leads to memory corruption and can cause the dnsmasq daemon to crash, resulting in a denial-of-service condition.
This flaw, rated HIGH with a CVSS score of 7.5, presents a significant risk to network availability. While the National Vulnerability Database has not specified affected products beyond dnsmasq itself, any environment utilizing this DHCP and DNS caching server, particularly with the --dhcp-split-relay configuration, is exposed. Defenders must prioritize patching dnsmasq instances or implementing strict network segmentation and traffic filtering to prevent the delivery of malformed BOOTREPLY packets.
What This Means For You
- If your organization uses dnsmasq, especially with the `--dhcp-split-relay` option enabled, you must immediately assess your exposure to CVE-2026-6507. Prioritize patching dnsmasq to the latest secure version. As a mitigating control, consider implementing network access controls or firewall rules to block unexpected or malformed BOOTREPLY packets from reaching your dnsmasq servers.
Related ATT&CK Techniques
🛡️ Detection Rules
2 rules · 6 SIEM formats2 detection rules auto-generated for this incident, mapped to MITRE ATT&CK. Sigma YAML is free — export to any SIEM format via the Intel Bot.
DoS Traffic Pattern Detection
Indicators of Compromise
| ID | Type | Indicator |
|---|---|---|
| CVE-2026-6507 | DoS | dnsmasq daemon crash |
| CVE-2026-6507 | Memory Corruption | dnsmasq out-of-bounds write vulnerability |
| CVE-2026-6507 | DoS | dnsmasq server configured with --dhcp-split-relay option |
| CVE-2026-6507 | Memory Corruption | Specially crafted BOOTREPLY (Bootstrap Protocol Reply) packet |
Written by SCW Vulnerability Desk
Source & Attribution
| Source Platform | NVD |
| Channel | National Vulnerability Database |
| Published | April 17, 2026 at 16:16 UTC |
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