CVE-2025-48990 is a high-severity heap-based buffer overflow vulnerability identified in version 0.0.2 of NeKernal, a free and open-source operating system stack. The flaw exists in the function rt_copy_memory, which unconditionally writes a null terminator byte ('\0') at the position dst[len]. When the length parameter len equals the size of the destination buffer (256 bytes), this write operation causes a one-byte overflow beyond the allocated buffer boundary. This off-by-one overflow can corrupt adjacent heap memory, potentially leading to undefined behavior such as memory corruption, application crashes, or exploitation for arbitrary code execution. The vulnerability is classified under CWE-122 (Heap-based Buffer Overflow). The patch approach taken was minimalistic: the overflow-causing line was removed without adding bounds checking or changing the function signature, to maintain backward compatibility. The CVSS 4.0 base score is 8.6 (high severity), reflecting that the vulnerability requires local access (Attack Vector: Local), low attack complexity, no privileges or user interaction, but has high impact on confidentiality, integrity, and availability. No known exploits are reported in the wild yet. The vulnerability affects only version 0.0.2 of NeKernal, and the issue was published on June 2, 2025. Given the nature of the vulnerability, an attacker with local access could leverage this overflow to manipulate heap memory, potentially leading to privilege escalation or denial of service within systems running this OS stack.

For European organizations, the impact depends largely on the adoption of NeKernal OS within their infrastructure. While NeKernal is an open-source OS stack and may be used in specialized or embedded environments, any deployment in critical systems could be at risk. Exploitation could lead to local privilege escalation, allowing attackers to gain unauthorized access or control over affected systems. This could compromise confidentiality of sensitive data, integrity of system operations, and availability of services. In sectors such as industrial control, telecommunications, or research institutions where custom or niche OS stacks might be deployed, the vulnerability could disrupt operations or facilitate lateral movement by attackers. The lack of requirement for user interaction or privileges to exploit (beyond local access) increases risk in multi-user environments or where local access can be gained through other means. Although no known exploits exist yet, the high CVSS score and the nature of heap overflows warrant proactive mitigation to prevent potential future attacks.

European organizations using NeKernal 0.0.2 should immediately upgrade to a patched version once available, or apply the minimal patch that removes the overflow-causing line in rt_copy_memory. Since the patch does not add bounds checking, organizations should also conduct thorough code audits and implement additional memory safety checks around this function if possible. Employing runtime protections such as heap canaries, address space layout randomization (ASLR), and control-flow integrity (CFI) can help mitigate exploitation attempts. Restricting local access to trusted users and systems reduces the attack surface. For embedded or specialized deployments, consider isolating NeKernal-based systems within segmented network zones and monitoring for anomalous behavior indicative of exploitation attempts. Additionally, organizations should maintain up-to-date inventories of systems running NeKernal and conduct vulnerability scanning to identify affected versions. Incident response plans should include procedures for detecting and responding to heap overflow exploitation attempts.