CVE-2023-28846 Denial of Service in unpoly-rails
Attackers can cause denial of service by sending long URLs, triggering oversized headers that disable Rails instances behind passive health-check load balancers.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2023-28846?
CVE-2023-28846 is a medium-severity denial of service vulnerability in unpoly-rails, published on 30 Mar 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Unpoly is a JavaScript framework for server-side web applications. There is a possible Denial of Service (DoS) vulnerability in the `unpoly-rails` gem that implements the Unpoly server protocol for Rails applications. This issues affects Rails applications that operate as an upstream of a load balancer's that uses passive health checks. The `unpoly-rails` gem echoes the request URL as an `X-Up-Location` response header. By making a request with exceedingly long URLs (paths or query string), an attacker can cause unpoly-rails to write a exceedingly large response header. If the response header is too large to be parsed by a load balancer downstream of the Rails application, it may cause the load balancer to remove the upstream from a load balancing group. This causes that application instance to become unavailable until a configured timeout is reached or until an active healthcheck succeeds. This issue has been fixed and released as version 2.7.2.2 which is available via RubyGems and GitHub. Users unable to upgrade may: Configure your load balancer to use active health checks, e.g. by periodically requesting a route with a known response that indicates healthiness; Configure your load balancer so the maximum size of response headers is at least twice the maximum size of a URL; or instead of changing your server configuration you may also configure your Rails application to delete redundant `X-Up-Location` headers set by unpoly-rails.
Weakness: CWE-400
Which versions are affected by CVE-2023-28846?
2 open source packages ship an affected version, including unpoly-rails. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
unpoly-rails RubyGems | All versions | 2.7.2.2 |
unpoly-rails RubyGems | All versions | 2.7.2.2 |
Products include Unpoly Unpoly-Rails.
How do I fix CVE-2023-28846?
Upgrade unpoly-rails to 2.7.2.2 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2023-28846 being exploited?
There is no known exploitation of CVE-2023-28846 in the wild and no public exploit code.
Sources
Also known as GHSA-m875-3xf6-mf78.