{"schema_version":"1.7.3","id":"GHSA-625h-95r8-8xpm","published":"2025-09-25T16:39:27Z","modified":"2026-04-04T06:15:08.709685092Z","aliases":["CVE-2025-59830"],"related":["CGA-8fhh-662x-5cqf"],"summary":"Rack has an unsafe default in Rack::QueryParser allows params_limit bypass via semicolon-separated parameters","details":"## Summary\n\n`Rack::QueryParser` in version `< 2.2.18` 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.\n\n## Details\n\nThe issue arises because `Rack::QueryParser#check_query_string` counts only `&` characters when determining the number of parameters, but the default separator regex `DEFAULT_SEP = /[&;] */n` splits on both `&` and `;`. This mismatch means that queries using `;` separators were not included in the parameter count, allowing `params_limit` to be bypassed.\n\nOther safeguards (`bytesize_limit` and `key_space_limit`) still applied, but did not prevent this particular bypass.\n\n## Impact\n\nApplications 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.\n\n`Rack::Request`, the primary entry point for typical Rack applications, uses `QueryParser` in a safe way and does not appear vulnerable by default. As such, the severity is considered **low**, with the impact limited to edge cases where `QueryParser` is used directly.\n\n## Mitigation\n\n* Upgrade to a patched version of Rack where both `&` and `;` are counted consistently toward `params_limit`.\n* If upgrading is not immediately possible, configure `QueryParser` with an explicit delimiter (e.g., `&`) to avoid the mismatch.\n* As a general precaution, enforce query string and request size limits at the web server or proxy layer (e.g., Nginx, Apache, or a CDN) to mitigate excessive parsing overhead.","affected":[{"package":{"name":"rack","ecosystem":"RubyGems","purl":"pkg:gem/rack"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.2.18"}]}],"versions":["0.1.0","0.2.0","0.3.0","0.4.0","0.9.0","0.9.1","1.0.0","1.0.1","1.1.0","1.1.1","1.1.1.pre","1.1.2","1.1.3","1.1.4","1.1.5","1.1.6","1.2.0","1.2.1","1.2.2","1.2.3","1.2.4","1.2.5","1.2.6","1.2.7","1.2.8","1.3.0","1.3.0.beta","1.3.0.beta2","1.3.1","1.3.10","1.3.2","1.3.3","1.3.4","1.3.5","1.3.6","1.3.7","1.3.8","1.3.9","1.4.0","1.4.1","1.4.2","1.4.3","1.4.4","1.4.5","1.4.6","1.4.7","1.5.0","1.5.0.beta.1","1.5.0.beta.2","1.5.1","1.5.2","1.5.3","1.5.4","1.5.5","1.6.0","1.6.0.beta","1.6.0.beta2","1.6.1","1.6.10","1.6.11","1.6.12","1.6.13","1.6.2","1.6.3","1.6.4","1.6.5","1.6.6","1.6.7","1.6.8","1.6.9","2.0.0.alpha","2.0.0.rc1","2.0.1","2.0.2","2.0.3","2.0.4","2.0.5","2.0.6","2.0.7","2.0.8","2.0.9","2.0.9.1","2.0.9.2","2.0.9.3","2.0.9.4","2.1.0","2.1.1","2.1.2","2.1.3","2.1.4","2.1.4.1","2.1.4.2","2.1.4.3","2.1.4.4","2.2.0","2.2.1","2.2.10","2.2.11","2.2.12","2.2.13","2.2.14","2.2.15","2.2.16","2.2.17","2.2.2","2.2.3","2.2.3.1","2.2.4","2.2.5","2.2.6","2.2.6.1","2.2.6.2","2.2.6.3","2.2.6.4","2.2.7","2.2.8","2.2.8.1","2.2.9"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2025/09/GHSA-625h-95r8-8xpm/GHSA-625h-95r8-8xpm.json"}}],"references":[{"type":"WEB","url":"https://github.com/rack/rack/security/advisories/GHSA-625h-95r8-8xpm"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-59830"},{"type":"WEB","url":"https://github.com/rack/rack/commit/54e4ffdd5affebcb0c015cc6ae74635c0831ed71"},{"type":"PACKAGE","url":"https://github.com/rack/rack"}],"database_specific":{"cwe_ids":["CWE-400","CWE-770"],"github_reviewed":true,"github_reviewed_at":"2025-09-25T16:39:27Z","nvd_published_at":"2025-09-25T15:16:13Z","severity":"HIGH"},"severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"}]}