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CVE-2023-28846 Detail


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 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.


CVSS 3.x Severity and Metrics:

Base Score:  7.5 HIGH
Vector:  CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Nist CVSS score does not match with CNA score
CNA:  GitHub, Inc.
Base Score:  5.9 MEDIUM
Vector:  CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

NVD Analysts use publicly available information to associate vector strings and CVSS scores. We also display any CVSS information provided within the CVE List from the CNA.

Note: It is possible that the NVD CVSS may not match that of the CNA. The most common reason for this is that publicly available information does not provide sufficient detail or that information simply was not available at the time the CVSS vector string was assigned.

References to Advisories, Solutions, and Tools

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Hyperlink Resource
https://docs.nginx.com/nginx/admin-guide/load-balancer/http-health-check/#passive-health-checks Technical Description 
https://github.com/unpoly/unpoly-rails/ Product 
https://github.com/unpoly/unpoly-rails/commit/cd9ad0007daceeb3b2354fdcab4f88350427bf16 Patch  Vendor Advisory 
https://github.com/unpoly/unpoly-rails/security/advisories/GHSA-m875-3xf6-mf78 Vendor Advisory 
https://makandracards.com/operations/537537-nginx-proxy-buffer-tuning Third Party Advisory 
https://tryhexadecimal.com/guides/http/414-request-uri-too-long Third Party Advisory 
https://unpoly.com/up.protocol Product 

Weakness Enumeration

CWE-ID CWE Name Source
CWE-400 Uncontrolled Resource Consumption Provider acceptance level GitHub, Inc.  

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Change History

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Quick Info

CVE Dictionary Entry:
NVD Published Date:
NVD Last Modified:
GitHub, Inc.