ADVISORIES
GEM
SEVERITY
CVSS v3.x: 7.5 (High)
PATCHED VERSIONS
- ~> 2.2.14
- ~> 3.0.16
- >= 3.1.14
DESCRIPTION
Summary
Rack::QueryParser
parses query strings and
application/x-www-form-urlencoded
bodies into Ruby data structures
without imposing any limit on the number of parameters, allowing
attackers to send requests with extremely large numbers of parameters.
Details
The vulnerability arises because Rack::QueryParser
iterates over
each &
-separated key-value pair and adds it to a Hash without
enforcing an upper bound on the total number of parameters. This
allows an attacker to send a single request containing hundreds of
thousands (or more) of parameters, which consumes excessive memory
and CPU during parsing.
Impact
An attacker can trigger denial of service by sending specifically crafted HTTP requests, which can cause memory exhaustion or pin CPU resources, stalling or crashing the Rack server. This results in full service disruption until the affected worker is restarted.
Mitigation
- Update to a version of Rack that limits the number of parameters parsed, or
- Use middleware to enforce a maximum query string size or parameter count, or
- Employ a reverse proxy (such as Nginx) to limit request sizes and reject oversized query strings or bodies.
Limiting request body sizes and query string lengths at the web server or CDN level is an effective mitigation.
RELATED
- https://nvd.nist.gov/vuln/detail/CVE-2025-46727
- https://github.com/rack/rack/security/advisories/GHSA-gjh7-p2fx-99vx
- https://github.com/rack/rack/commit/2bb5263b464b65ba4b648996a579dbd180d2b712
- https://github.com/rack/rack/commit/3f5a4249118d09d199fe480466c8c6717e43b6e3
- https://github.com/rack/rack/commit/cd6b70a1f2a1016b73dc906f924869f4902c2d74
- https://github.com/advisories/GHSA-gjh7-p2fx-99vx