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High, CVSS 7.5

Circumvention of file size limits in ActiveStorage

CVE-2020-8162GHSA-m42x-37p3-fv5w

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (activestorage 6.0.3.1, 5.2.4.3), 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

  • RubyGems activestorage

    Affected
    >= 5.0.0, <= 5.2.4.2>= 6.0.0, <= 6.0.3
    Fixed in
    6.0.3.1, 5.2.4.3

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
EPSS
  • CVE-2020-8162: 3.03% estimated exploitation activity in the next 30 days; percentile 87.49 (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.

There is a vulnerability in ActiveStorage's S3 adapter that allows the Content-Length of a direct file upload to be modified by an end user. Versions Affected: rails < 5.2.4.2, rails < 6.0.3.1 Not affected: Applications that do not use the direct upload functionality of the ActiveStorage S3 adapter. Fixed Versions: rails = 5.2.4.3, rails = 6.0.3.1 Impact ------ Utilizing this vulnerability, an attacker can control the Content-Length of an S3 direct upload URL without receiving a new signature from the server. This could be used to bypass controls in place on the server to limit upload size. Workarounds ----------- This is a low-severity security issue. As such, no workaround is necessarily until such time as the application can be upgraded.

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

    Published from ghsa record GHSA-m42x-37p3-fv5w

Agent brief

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# Patch Next advisory brief: CVE-2020-8162

Advisory: Circumvention of file size limits in ActiveStorage
IDs: CVE-2020-8162, GHSA-m42x-37p3-fv5w
Record: https://patchnext.com/advisories/cve-2020-8162 (revision 1, source checked 26 Oct 2026, 15:47 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: activestorage 6.0.3.1, 5.2.4.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems activestorage: affected >= 5.0.0, <= 5.2.4.2; >= 6.0.0, <= 6.0.3; fixed in 6.0.3.1, 5.2.4.3

## Suggested inspection (read-only)
- RubyGems activestorage: 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 activestorage.
- 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-m42x-37p3-fv5w (GitHub-reviewed advisory GHSA-m42x-37p3-fv5w lists affected ranges: RubyGems activestorage >=5.0.0 =6.0.0 <=6.0.3)

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