CVE-2020-8162: Circumvention of file size limits in ActiveStorage

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 3.0% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2020-06-19 · updated 2026-06-17
Weakness: CWE-602

Description

A client side enforcement of server side security vulnerability exists in rails < 5.2.4.2 and rails < 6.0.3.1 ActiveStorage's S3 adapter that allows the Content-Length of a direct file upload to be modified by an end user bypassing upload limits.

Affected products

Debian Linux: 10.0
Ruby on Rails: before 5.2.4.2; from 6.0.0 before 6.0.3.1 — fixed in 5.2.4.2, 6.0.3.1
Rubygems Activestorage: from 5.0.0 before 5.2.4.3; from 6.0.0 before 6.0.3.1; 5.2.0, 5.2.0.beta1, 5.2.0.beta2, 5.2.0.rc1, 5.2.0.rc2, 5.2.1 (+21) — fixed in 5.2.4.3, 6.0.3.1

How to fix

Upgrade to a fixed version: Ruby on Rails 5.2.4.2, 6.0.3.1; Rubygems Activestorage 5.2.4.3, 6.0.3.1. Check the vendor advisory for mitigations.

References

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