Description

Integer underflow (wrap or wraparound) in DNS Server allows an unauthorized attacker to execute code over a network.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "9.8",
  "pubDate": "2026-10-13T19:20:36.677Z",
  "pubdate": "2026-10-13T19:20:36.677Z",
  "executiveSummary": "This vulnerability involves an integer underflow condition within the DNS Server software, which can be leveraged by an unauthenticated, remote attacker to achieve arbitrary code execution.\nThe vulnerability type is categorized as an integer underflow, also known as an integer wraparound, which occurs when a mathematical operation produces a value smaller than the minimum representable integer for the assigned data type.\nThe primary impact of successful exploitation is remote code execution, granting the attacker the ability to execute unauthorized instructions with the privileges of the DNS service process.\nAffected systems include the DNS Server component. The risk profile is critical, as it allows for full compromise of the affected service without the need for prior authentication or local access.\nAttackers can trigger this vulnerability over a network by sending specifically crafted packets to the target service. The exploitation requirement is successful manipulation of input data that influences a length calculation or memory offset, resulting in an out-of-bounds memory operation.\nDue to the nature of DNS services typically operating with elevated system or network-level privileges, this vulnerability presents a significant threat to internal infrastructure integrity and availability.",
  "technicalDetails": "The root cause of this vulnerability lies in an improper handling of arithmetic operations during the processing of DNS packets within the DNS Server component. Specifically, an integer underflow occurs when a length value or offset calculation, derived from user-supplied network data, is decremented below zero without adequate boundary validation.\nIn a C/C++ environment, this underflow typically results in the wrapping of an unsigned integer variable to its maximum possible value (e.g., 0 minus 1 becomes 0xFFFFFFFF for a 32-bit unsigned integer). If this resulting large integer is subsequently used to define the size of a memory allocation, a copy operation, or a pointer arithmetic offset, it leads to an out-of-bounds memory access.\nThe attack flow initiates when the DNS Server receives a malicious packet containing crafted fields designed to trigger the underflow during internal parsing or decoding logic. The server, failing to account for potential underflow scenarios, uses the wrapped, excessively large value as a parameter for sensitive functions such as memcpy(), memmove(), or pointer indexing.\nBy manipulating the length or offset, an attacker can induce a heap or stack-based buffer overflow. If the overflow overwrites critical control structures, such as return addresses on the stack, function pointers in a vtable, or entry points in the Global Offset Table (GOT), the attacker gains control over the instruction pointer.\nExploitation requires no authentication and is feasible over a network connection, as the DNS Server is typically exposed to receive and process recursive or iterative queries. The payload behavior involves the delivery of shellcode or a ROP (Return-Oriented Programming) chain, which allows the attacker to bypass modern exploit mitigations like DEP (Data Execution Prevention) and ASLR (Address Space Layout Randomization).\nPost-exploitation, the attacker operates with the same privilege level as the DNS process. Given that DNS servers often run as system-level services, this frequently results in full system compromise, the ability to intercept or redirect network traffic, or the establishment of a persistent backdoor within the network infrastructure."
}