CVE-2020-8165 ActiveSupport potentially unintended unmarshalling of user-provided objects in MemCacheStore and RedisCacheStore

Q: Which versions are affected by CVE-2020-8165?

4 open source packages ship an affected version, including activesupport. It affects 3 products.

Q: Is CVE-2020-8165 being exploited?

There is no known exploitation of CVE-2020-8165 in the wild and no public exploit code.

Q: How do I fix CVE-2020-8165?

Upgrade activesupport to a fixed version for your release line: 5.2.4.3 or 6.0.3.1.

Critical 9.8 Published 19 Jun 2020 Updated 9 May 2025

Attackers can achieve remote code execution by exploiting unsafe deserialization in Rails cache stores when using MemCache or Redis.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2020-8165?

CVE-2020-8165 is a critical unsafe deserialization vulnerability in Debian Debian Linux, published on 19 Jun 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

A deserialization of untrusted data vulnernerability exists in rails < 5.2.4.3, rails < 6.0.3.1 that can allow an attacker to unmarshal user-provided objects in MemCacheStore and RedisCacheStore potentially resulting in an RCE.

Weakness: CWE-502

Which versions are affected by CVE-2020-8165?

4 open source packages ship an affected version, including activesupport. It affects 3 products.

Package	Affected	Fixed in
`activesupport` RubyGems	From `5.0.0`	`5.2.4.3`
`activesupport` RubyGems	From `5.0.0`	`5.2.4.3`
`activesupport` RubyGems	From `6.0.0`	`6.0.3.1`
`activesupport` RubyGems	From `6.0.0`	`6.0.3.1`

Linux distribution packages (8)

`rubygem-activesupport-5_1` SUSE:Linux Enterprise High Availability Extension 15	All versions	`5.1.4-3.3.1`
`rubygem-activesupport-5_1` SUSE:Linux Enterprise High Availability Extension 15 SP1	All versions	`5.1.4-3.3.1`
`rubygem-activesupport-5_1` SUSE:Linux Enterprise High Availability Extension 15 SP2	All versions	`5.1.4-3.3.1`
`rubygem-activesupport-4_2` SUSE:OpenStack Cloud 7	All versions	`4.2.9-7.9.1`
`rubygem-activesupport-4_2` SUSE:OpenStack Cloud Crowbar 8	All versions	`4.2.9-7.9.1`
`rubygem-activesupport-4_2` SUSE:OpenStack Cloud Crowbar 9	All versions	`4.2.9-7.9.1`
`rubygem-activesupport-5_1` openSUSE:Leap 15.1	All versions	`5.1.4-lp151.3.3.1`
`rubygem-activesupport-5_1` openSUSE:Leap 15.2	All versions	`5.1.4-lp152.4.3.1`

Products include Debian Debian Linux, Opensuse Leap, Rubyonrails Rails.

How do I fix CVE-2020-8165?

Upgrade activesupport to a fixed version for your release line: 5.2.4.3 or 6.0.3.1.

Upgrade, and only deserialise data from trusted sources or with an allow-list of types. More about Unsafe deserialization.

Is CVE-2020-8165 being exploited?

There is no known exploitation of CVE-2020-8165 in the wild and no public exploit code.

Public exploit code: 7 proofs of concept on GitHub.

All Debian Debian Linux vulnerabilities

Sources

Also known as DEBIAN-CVE-2020-8165, GHSA-2p68-f74v-9wc6, SUSE-SU-2020:2899-1, SUSE-SU-2020:2929-1, UBUNTU-CVE-2020-8165, openSUSE-SU-2020:1677-1 and 1 more.