CVE-2026-4892
Description
A heap buffer overflow was discovered in dnsmasq's DHCP script helper process. When processing DHCPv6 client identifiers (CLIDs), the helper hex-encodes the raw CLID bytes into a fixed-size buffer without length validation. Since DHCPv6 CLIDs can be up to 65,535 bytes, a crafted DHCPv6 packet can overflow the buffer with attacker-controlled content. The helper process runs with root privileges.
Statement
Red Hat rates this as Important. The overflow occurs in a root-privileged helper process with attacker-controlled content, and the --dhcp-script option is enabled by default in libvirt virtual network configurations, which affects RHEL systems using virt-manager, virt-install, or cockpit-machines. Exploitation requires the attacker to send crafted DHCPv6 packets from within the virtual network, meaning a malicious VM guest could potentially exploit this for host-level code execution as root.
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 | 8.8 | N/A | 8.8 |
| Attack Vector | Adjacent Network | N/A | Adjacent 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 | High | N/A | High |
| Integrity Impact | High | N/A | High |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
cve.org: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
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