Cybersecurity experts have highlighted the rising threat of subdomain takeovers fueled by improperly managed Domain Name System (DNS) records a vulnerability known as “Dangling DNS.”
This technique allows attackers to hijack unused or misconfigured subdomains, posing significant risks to organizations and their supply chains.
A subdomain takeover occurs when an attacker gains control of a subdomain that has been left exposed due to configuration errors, abandonment, or deprovisioned resources.
For example, DNS records, including canonical name (CNAME), A, or MX records, may still direct traffic to resources that no longer exist or have been repurposed, creating an exploitable opening.
Attackers exploit this oversight to register the targeted subdomain under their control, replacing legitimate content with harmful or unauthorized material.
SaaS Platforms and Cloud Services at Risk
The risk is particularly pronounced for subdomains linked to third-party Software-as-a-Service (SaaS) providers or cloud platforms.
As businesses evolve and migrate between services, they often fail to update or remove outdated DNS configurations.
For instance, subdomains such as support.YourBiz.com, linked to a deprecated helpdesk SaaS platform (e.g., Zendesk), are prime targets.
In some cases, attackers exploit free cloud service trials to gain control over discarded subdomains, further amplifying the risk.
Similarly, in cloud computing environments, subdomains pointing to deleted resources such as Amazon S3 storage buckets, load balancers, or web applications are frequently left unmodified in DNS settings.
This oversight enables attackers to establish malicious replacements under the original subdomain.
A study found hundreds of S3 buckets with lingering DNS pointers, exposing enterprises to attacks aimed at defacing websites, phishing, malware distribution, or stealing user credentials.
Real-World Impact and Supply Chain Risks
The implications of these takeovers go beyond immediate reputational damage or phishing attacks. They can cascade into severe supply chain risks.
In one investigation conducted between late 2024 and early 2025, researchers reportedly took control of 150 abandoned Amazon S3 buckets referenced by subdomains originating from government agencies, Fortune 500 companies, and critical open-source projects.
Within four months, the researchers observed over 8 million live requests directed toward these compromised subdomains, including requests for container images, software updates, and precompiled binaries.
Such scenarios present grave risks, particularly if compromised subdomains serve as a delivery point for sensitive artifacts.
For example, attackers might manipulate configurations to inject malicious code into widely used software, spreading malware or enabling remote code execution (RCE).
The possibility of tampering with SSLVPN server settings or pipeline deployment artifacts highlights the sophistication and potential scale of these exploitations.
To mitigate the risk of Dangling DNS vulnerabilities, organizations should implement a layered security approach across their software development lifecycle.
Proactive identification of misconfigured DNS records and deprovisioned cloud resources is essential.
SentinelOne, for instance, has alerted clients to over 1,250 subdomain takeover risks related to deprovisioned cloud resources in the past year, along with additional vulnerabilities stemming from other overlooked DNS configurations.
Automated tools and offensive security engines can also help identify and prioritize remediation efforts for these risks.
According to the Report, From an operational standpoint, security teams must maintain up-to-date inventories of DNS records and ensure swift remediation upon resource decommissioning.
Routine audits, especially for subdomains linked to SaaS applications or cloud services, are critical to closing these gaps.
Subdomain takeovers underscore how seemingly low-priority misconfigurations can evolve into critical vulnerabilities with far-reaching implications.
As attackers continue to exploit Dangling DNS, organizations must remain vigilant in monitoring their digital assets.
By adopting a proactive, security-first mindset that includes runtime protection, businesses can safeguard their infrastructure and minimize exposure to cascading supply chain risks.
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