Recent analyses have revealed a notable increase in scanning activities aimed at SonicWall firewall management interfaces, suggesting potential reconnaissance for undisclosed vulnerabilities. This surge has prompted cybersecurity experts to advise caution as they monitor these developments closely.
Significant Increase in Scanning Activity
Between May 9 and May 18, 2026, GreyNoise, a threat intelligence company, reported a substantial rise in the scanning of SonicWall SonicOS management APIs. The most significant spike occurred on May 12, with approximately 597,000 sessions recorded, marking a 46-fold increase compared to the average daily activity in the previous month.
This unprecedented volume suggests coordinated efforts to probe exposed firewall interfaces, potentially indicating a preparatory phase for exploiting new vulnerabilities. The activity on that day set a record for the single-day volume observed in the last 90 days under the SonicWall SonicOS API Scanner category.
Patterns and Potential Implications
GreyNoise researchers noted that a similar pattern was observed earlier this year before the announcement of a specific SonicWall vulnerability, CVE-2026-0400, on February 24, 2026. Previous spikes on January 18, January 30, and February 14 occurred days before that disclosure, hinting at a recurring pattern of heightened activity preceding vulnerability announcements.
Although this does not confirm the existence of a new vulnerability, it underscores the need for vigilance as hackers could be in the early stages of reconnaissance. The consistency in scanning tools and infrastructure, such as the use of a Chrome 119 user-agent on Linux x86_64 by 99% of requests, aligns with previous campaigns.
Recommended Security Measures
Security teams managing SonicWall devices are urged to take immediate actions to minimize exposure. Recommended measures include restricting access to SonicOS management APIs and SSL VPNs to trusted IP ranges, removing public access to management interfaces, enforcing multi-factor authentication for all VPN users, auditing for unauthorized accounts created after May 1, 2026, and using dynamic IP blocklists to deter known threats.
Short-term monitoring should involve keeping abreast of SonicWall PSIRT advisories for any new disclosures, being ready to apply patches within 24 hours of release, and enhancing log retention with alerting for unusual outbound activities.
While no new vulnerabilities have been confirmed, the scale of these scanning activities serves as a cautionary signal for cybersecurity defenders. Proactive system hardening, continuous monitoring, and quick patching are essential strategies to mitigate risks associated with potential SonicWall infrastructure exposure.
