Denial of service in activestorage gem for Ruby

1) Input validation error

EUVDB-ID: #VU28240

Risk: Medium

CVSSv4.0: 2.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2020-8162

CWE-ID: CWE-20 - Improper input validation

Exploit availability: No

Description

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.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

activestorage: 5.2.0.beta1 - 6.0.3 rc1

CPE2.3

• cpe:2.3:a:ruby:activestorage:5.2.0.beta1:*:*:*:*:rubygems:*:*
• cpe:2.3:a:ruby:activestorage:5.2.0.beta2:*:*:*:*:rubygems:*:*
• cpe:2.3:a:ruby:activestorage:5.2.0:*:*:*:*:rubygems:*:*

External links

https://snyk.io/vuln/SNYK-RUBY-ACTIVESTORAGE-569602
https://github.com/rails/rails/commit/c0ab9a7d29b84a6ccb1ffa3e8ca1ce61f7a9fbb8
https://groups.google.com/forum/#!topic/rubyonrails-security/PjU3946mreQ
https://hackerone.com/reports/789579

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.