CVE-2026-1425 is a stack-based buffer overflow vulnerability found in pymumu SmartDNS versions 47.0 and 47.1, affecting the SVBC Record Parser component within the src/dns.c file. The vulnerability arises from improper handling in the functions _dns_decode_rr_head and _dns_decode_SVCB_HTTPS, which parse DNS resource record headers and SVCB/HTTPS records respectively. An attacker can craft malicious DNS responses that exploit this flaw to overflow a stack buffer, potentially overwriting control data and enabling arbitrary code execution or causing a denial of service via application crash. The vulnerability is remotely exploitable without requiring authentication or user interaction, but the attack complexity is high due to the need for precise manipulation of DNS responses. The CVSS 4.0 vector indicates network attack vector, high attack complexity, no privileges or user interaction required, and low impact on confidentiality, integrity, and availability. No known exploits have been observed in the wild to date. The vendor has released a patch (commit 2d57c4b4e1add9b4537aeb403f794a084727e1c8) that addresses this issue by correcting the parsing logic to prevent buffer overflow conditions. Given the critical role of SmartDNS in DNS resolution and traffic routing, this vulnerability poses a risk to the stability and security of affected systems if left unpatched.

The vulnerability could allow remote attackers to execute arbitrary code or cause denial of service on systems running vulnerable versions of pymumu SmartDNS. This can disrupt DNS resolution services, impacting network availability and potentially enabling further compromise of internal networks or interception of DNS traffic. Organizations relying on SmartDNS for DNS acceleration or filtering may experience service outages or data integrity issues. Although exploitation complexity is high and no known exploits exist currently, the potential impact on confidentiality, integrity, and availability of DNS services is significant. Attackers could leverage this flaw to bypass DNS-based security controls or redirect traffic maliciously, affecting both enterprise and ISP environments. The medium CVSS score reflects moderate risk but warrants timely remediation due to the critical nature of DNS infrastructure.

Organizations should immediately apply the official patch identified by commit 2d57c4b4e1add9b4537aeb403f794a084727e1c8 to all affected pymumu SmartDNS instances. Network administrators should monitor DNS traffic for anomalous or malformed SVCB/HTTPS records that could indicate exploitation attempts. Deploying DNS security extensions (DNSSEC) and validating DNS responses can reduce the risk of malicious DNS data injection. Restricting external access to DNS resolver management interfaces and implementing network segmentation can limit exposure. Regularly updating and auditing DNS software versions and configurations will help prevent exploitation of similar vulnerabilities. Additionally, organizations should consider deploying intrusion detection systems with signatures for buffer overflow attempts targeting DNS parsers. Incident response plans should include procedures for DNS service recovery and forensic analysis in case of compromise.