DOM-based vulnerabilities arise when a client-side script reads data from a controllable part of the DOM (for example, the URL) and processes this data in an unsafe way.
DOM-based denial of service arises when a script passes controllable data to a problematic platform API in an unsafe way. An attacker may be able to use the vulnerability to construct a URL that, if visited by another application user, will cause a denial of service condition on the user's computer when the relevant API is invoked. Depending on the nature of the API, the invocation may cause the user's computer to consume excessive amounts of CPU or disk space. This may result in side effects if the web browser restricts application functionality; for example, by rejecting attempts to store data in localStorage or killing busy scripts.
Burp Suite automatically identifies this issue using static code analysis, which may lead to false positives that are not actually exploitable. The relevant code and execution paths should be reviewed to determine whether this vulnerability is indeed present, or whether mitigations are in place that would prevent exploitation.
The most effective way to avoid DOM-based denial of service vulnerabilities is not to dynamically pass data into problematic platform APIs that originated from any untrusted source. If the desired functionality of the application means that this behavior is unavoidable, then defenses must be implemented within the client-side code to prevent malicious data from causing a denial of service condition. In many cases, the relevant data can be validated on a whitelist basis, to allow only content that is known to be safe.