unpoly-rails Denial of Service vulnerability

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.9 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2023-28846: 1.03% estimated exploitation activity in the next 30 days; percentile 63.88 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

There is a possible Denial of Service (DoS) vulnerability in the unpoly-rails gem that implements the Unpoly server protocol for Rails applications. Impact 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. Patches The fixed release 2.7.2.2+ is available via RubyGems and GitHub. Workarounds If you cannot upgrade to a fixed release, several workarounds are…

Published by the source

30 Mar 2023, 22:58 UTC

Last modified by the source

7 Apr 2023, 22:54 UTC

Source last checked

26 Oct 2026, 15:44 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-m875-3xf6-mf78

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# Patch Next advisory brief: CVE-2023-28846

Advisory: unpoly-rails Denial of Service vulnerability
IDs: CVE-2023-28846, GHSA-m875-3xf6-mf78
Record: https://patchnext.com/advisories/cve-2023-28846 (revision 1, source checked 26 Oct 2026, 15:44 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: unpoly-rails 2.7.2.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems unpoly-rails: affected < 2.7.2.2; fixed in 2.7.2.2

## Suggested inspection (read-only)
- RubyGems unpoly-rails: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on unpoly-rails.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-m875-3xf6-mf78 (GitHub-reviewed advisory GHSA-m875-3xf6-mf78 lists affected ranges: RubyGems unpoly-rails >=0 <2.7.2.2)

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