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Denial of service via malicious preflight requests in github.com/rs/cors

CVE-2025-47908GHSA-mh55-gqvf-xfwm

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (github.com/rs/cors 1.11.0), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
not scored
EPSS
  • CVE-2025-47908: 0.63% estimated exploitation activity in the next 30 days; percentile 50.32 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Middleware causes a prohibitive amount of heap allocations when processing malicious preflight requests that include a Access-Control-Request-Headers (ACRH) header whose value contains many commas. This behavior can be abused by attackers to produce undue load on the middleware/server as an attempt to cause a denial of service.

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 1 · created ·

    Published from ghsa record GHSA-mh55-gqvf-xfwm

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2025-47908

Advisory: Denial of service via malicious preflight requests in github.com/rs/cors
IDs: CVE-2025-47908, GHSA-mh55-gqvf-xfwm
Record: https://patchnext.com/advisories/cve-2025-47908 (revision 1, source checked 26 Oct 2026, 15:10 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Unrated
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/rs/cors 1.11.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/rs/cors: affected >= 1.9.0, < 1.11.0; fixed in 1.11.0

## Suggested inspection (read-only)
- Go github.com/rs/cors: 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 github.com/rs/cors.
- 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-mh55-gqvf-xfwm (GitHub-reviewed advisory GHSA-mh55-gqvf-xfwm lists affected ranges: Go github.com/rs/cors >=1.9.0 <1.11.0)

Commands are suggestions: review each one before running it.

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