CVE-2026-1425 identifies a stack-based buffer overflow vulnerability in pymumu SmartDNS, a DNS resolution and caching software, affecting versions 47.0 and 47.1. The vulnerability resides in the SVBC Record Parser component, specifically within the functions _dns_decode_rr_head and _dns_decode_SVCB_HTTPS located in src/dns.c. These functions are responsible for parsing DNS resource records, including SVCB and HTTPS records. Improper handling of specially crafted DNS responses can lead to a stack-based buffer overflow, which may allow remote attackers to overwrite the stack memory. This could result in arbitrary code execution or cause the application to crash, leading to denial of service. The attack vector is network-based (AV:N), requiring no privileges (PR:N) or user interaction (UI:N), but the attack complexity is high (AC:H), indicating that exploitation requires significant effort or specific conditions. The vulnerability impacts confidentiality, integrity, and availability at a low level, as indicated by the CVSS vector. No known exploits have been reported in the wild, but a patch identified by commit 2d57c4b4e1add9b4537aeb403f794a084727e1c8 is available and should be applied promptly. Given the critical role of DNS in network operations, exploitation could disrupt DNS resolution services or enable further attacks if code execution is achieved.

For European organizations, this vulnerability poses a risk primarily to DNS infrastructure relying on pymumu SmartDNS versions 47.0 and 47.1. Successful exploitation could lead to denial of service by crashing DNS services, impacting network availability and business continuity. In worst cases, arbitrary code execution could allow attackers to compromise DNS servers, potentially redirecting traffic, intercepting sensitive data, or facilitating lateral movement within networks. This is particularly concerning for sectors dependent on reliable DNS, such as finance, telecommunications, and government services. The medium severity rating reflects the balance between the potential impact and the high complexity of exploitation. However, given the critical nature of DNS, even medium-severity vulnerabilities warrant timely remediation. The lack of known exploits reduces immediate risk but does not eliminate the threat, especially as attackers may develop exploits over time.

European organizations should immediately verify if pymumu SmartDNS versions 47.0 or 47.1 are in use within their DNS infrastructure. If so, they must apply the official patch referenced by commit 2d57c4b4e1add9b4537aeb403f794a084727e1c8 without delay. Network administrators should monitor DNS traffic for anomalies that could indicate exploitation attempts, such as malformed DNS responses or unusual query patterns targeting SVCB/HTTPS records. Implementing network-level protections like DNS response validation, rate limiting, and anomaly detection can help mitigate exploitation risks. Additionally, organizations should conduct regular vulnerability assessments and penetration tests focusing on DNS components. Segmentation of DNS servers and limiting their exposure to untrusted networks will reduce attack surface. Maintaining up-to-date backups and incident response plans specific to DNS service disruptions is also recommended.