Rack is a modular Ruby web server interface. Prior to versions 2.2.14, 3.0.16, and 3.1.14, `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. 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. 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. Versions 2.2.14, 3.0.16, and 3.1.14 fix the issue. Some other mitigations are available. One may 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.
CVSS Score
7.5
EPSS Score
0.003
Published
2025-05-07
Rack is a modular Ruby web server interface. Carefully crafted content type headers can cause Rack’s media type parser to take much longer than expected, leading to a possible denial of service vulnerability (ReDos 2nd degree polynomial). This vulnerability is patched in 3.0.9.1 and 2.2.8.1.
CVSS Score
5.3
EPSS Score
0.003
Published
2024-02-29
Rack is a modular Ruby web server interface. Carefully crafted Range headers can cause a server to respond with an unexpectedly large response. Responding with such large responses could lead to a denial of service issue. Vulnerable applications will use the `Rack::File` middleware or the `Rack::Utils.byte_ranges` methods (this includes Rails applications). The vulnerability is fixed in 3.0.9.1 and 2.2.8.1.
CVSS Score
5.8
EPSS Score
0.003
Published
2024-02-29
A DoS vulnerability exists in Rack <v3.0.4.2, <v2.2.6.3, <v2.1.4.3 and <v2.0.9.3 within in the Multipart MIME parsing code in which could allow an attacker to craft requests that can be abuse to cause multipart parsing to take longer than expected.
CVSS Score
7.5
EPSS Score
0.021
Published
2023-03-10
A denial of service vulnerability in the Range header parsing component of Rack >= 1.5.0. A Carefully crafted input can cause the Range header parsing component in Rack to take an unexpected amount of time, possibly resulting in a denial of service attack vector. Any applications that deal with Range requests (such as streaming applications, or applications that serve files) may be impacted.
CVSS Score
7.5
EPSS Score
0.024
Published
2023-02-09