Denial of service in activestorage gem for Ruby

Published: 2020-05-26
Risk Medium
Patch available YES
Number of vulnerabilities 1
CVE ID CVE-2020-8162
Exploitation vector Network
Public exploit N/A
Vulnerable software
Web applications / Modules and components for CMS

Vendor Ruby

Security Advisory

This security advisory describes one medium risk vulnerability.

1) Input validation error

Risk: Medium

CVSSv3: 4.6 [CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L/E:U/RL:O/RC:C] [PCI]

CVE-ID: CVE-2020-8162

CWE-ID: CWE-20 - Improper Input Validation

Exploit availability: No


The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to insufficient validation of user-supplied input in ActiveStorage's S3 adapter. A remote attacker can control the Content-Length of an S3 direct upload URL without receiving a new signature from the server and perform a denial of service (DoS) attack.


Install updates from vendor's website.

Vulnerable software versions

activestorage: 5.2.0, 5.2.0.beta1, 5.2.0.beta2, 5.2.0.rc1, 5.2.0.rc2, 5.2.1,, 5.2.1.rc1, 5.2.2,, 5.2.2.rc1, 5.2.3, 5.2.3.rc1, 5.2.4,,, 5.2.4.rc1, 6.0.0, 6.0.0.beta1, 6.0.0.beta2, 6.0.0.beta3, 6.0.0.rc1, 6.0.0.rc2, 6.0.1, 6.0.1.rc1, 6.0.2,,, 6.0.2.rc1, 6.0.2.rc2, 6.0.3, 6.0.3.rc1

CPE External links!topic/rubyonrails-security/PjU3946mreQ

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.