CVE-2026-110912 in DragonFly BSD
Summary
by MITRE • 10/15/2026
In DragonFly BSD through 6.4.2 before 4bb22ff, the ARP input handlers arpintr() and in_arpinput() (sys/netinet/if_ether.c) do not validate the hardware address length (ar_hln) and protocol address length (ar_pln) fields of incoming ARP packets. in_arpreply() then uses these attacker-controlled values as memcpy lengths when copying from kernel buffers that are only 6 and 4 bytes long, resulting in an out-of-bounds read of kernel heap and stack memory that is copied into the ARP reply sent back to the requester. An unauthenticated attacker on the adjacent network can use a single crafted ARP request to disclose up to roughly 250 bytes of each type of kernel memory, including kernel pointers. This is expected to be fixed in the 6.6 stable release when that is available.
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Analysis
by VulDB Data Team • 10/15/2026
The vulnerability identified in DragonFly BSD versions prior to commit 4bb22ff represents a critical security flaw within the Address Resolution Protocol implementation, specifically affecting the input handlers arpintr() and in_arpinput located in sys/netinet/if_ether.c. The core technical deficiency lies in the failure of these functions to validate the hardware address length field, known as ar_hln, and the protocol address length field, known as ar_pln, contained within incoming ARP request packets. In a properly secured network stack, these fields must be rigorously checked against expected maximums corresponding to standard Ethernet addresses and IPv4 addresses before being utilized for memory operations. By omitting this validation step, the system accepts arbitrary values from untrusted external sources without verifying their legitimacy or safety relative to internal buffer constraints.
This lack of input sanitization directly leads to a severe out-of-bounds read condition when processing ARP replies via the in_arpreply() function. The attacker-controlled ar_hln and ar_pln values are passed as length parameters to memcpy operations that target kernel buffers with fixed, small sizes of six bytes for hardware addresses and four bytes for protocol addresses. When an adversary crafts a malicious ARP request specifying lengths significantly larger than these limits, the memory copy operation proceeds beyond the allocated boundaries. This results in reading arbitrary data from adjacent regions of kernel heap and stack memory, which are then inadvertently included in the ARP reply packet sent back to the requesting host.
The operational impact of this vulnerability is substantial due to its potential for information disclosure. An unauthenticated attacker positioned on an adjacent network segment can exploit this flaw with a single crafted ARP request to exfiltrate approximately two hundred and fifty bytes from each type of kernel memory space. This leakage includes sensitive data such as kernel pointers, which are crucial for bypassing modern security mitigations like Address Space Layout Randomization. The ability to leak these specific values facilitates further exploitation chains, including return-oriented programming attacks or direct kernel code execution, thereby compromising the integrity and confidentiality of the entire system.
From a classification perspective, this vulnerability aligns with CWE-125, which describes Out-of-bounds Read vulnerabilities where software reads data past the end or before the beginning of the intended buffer. Furthermore, it maps to MITRE ATT&CK technique T1087, specifically Account Discovery and OS Credential Dumping variants that rely on local information gathering through memory inspection. The exploitation vector is classified as Network-based with an Attack Complexity of Low, allowing remote attackers to trigger the flaw without prior authentication or complex setup procedures beyond crafting a single packet.
Mitigation strategies primarily involve applying the vendor-provided patch associated with commit 4bb22ff, which introduces proper validation checks for ar_hln and ar_pln fields before they are used in memory copy operations. Until such updates are available through the DragonFly BSD stable release channels, administrators should consider network segmentation to isolate systems from untrusted adjacent networks or deploy intrusion detection signatures that identify anomalous ARP packet structures with unusual address length fields. Additionally, enabling strict source validation mechanisms and monitoring for unexpected kernel memory leaks can help detect exploitation attempts in real-time while permanent fixes are deployed.