CVE-2025-59830

Rack is a modular Ruby web server interface. Prior to version 2.2.18, Rack::QueryParser enforces its params_limit only for parameters separated by &, while still splitting on both & and ;. As a result, attackers could use ; separators to bypass the parameter count limit and submit more parameters than intended. Applications or middleware that directly invoke Rack::QueryParser with its default configuration (no explicit delimiter) could be exposed to increased CPU and memory consumption. This can be abused as a limited denial-of-service vector. This issue has been patched in version 2.2.18.

Weakness

The product does not properly control the allocation and maintenance of a limited resource.

Affected Software

Potential Mitigations

• Mitigation of resource exhaustion attacks requires that the target system either:

• The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question.

• The second solution is simply difficult to effectively institute – and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/147.html
• https://cwe.mitre.org/data/definitions/227.html
• https://cwe.mitre.org/data/definitions/492.html

References

• https://github.com/rack/rack/commit/54e4ffdd5affebcb0c015cc6ae74635c0831ed71
• https://github.com/rack/rack/security/advisories/GHSA-625h-95r8-8xpm