How severe is CVE-2020-8165?

CVE-2020-8165 has a CVSS score of 9.8/10, rated CRITICAL. Immediate patching is strongly recommended.

Which packages are affected by CVE-2020-8165?

CVE-2020-8165 affects the following packages: activesupport (RubyGems), activesupport (RubyGems). Ecosystems affected: RubyGems.

How do I fix CVE-2020-8165?

Update activesupport to version 5.2.4.3 or later. Run your dependency manager's update command and verify no transitive dependencies pin the vulnerable version. Use O3 Security's SCA scanner to confirm the fix is applied across your entire dependency tree.

Is CVE-2020-8165 actively exploited in the wild?

Yes. There are 5 known exploit references for CVE-2020-8165, including 3 in-the-wild exploitations observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2020-8165?

CVE-2020-8165 has an EPSS (Exploit Prediction Scoring System) score of 90.1%, placing it in the 100th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. A score above 50% indicates significantly elevated exploitation risk — immediate patching is strongly recommended.

What type of vulnerability is CVE-2020-8165?

CVE-2020-8165 is classified as Deserialization of Untrusted Data (CWE-502). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2020-8165 published, and has it been updated?

CVE-2020-8165 was published on June 19, 2020 and was last updated on April 10, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

💎 RubyGems

CVE-2020-8165

CRITICAL

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

Also known asGHSA-2p68-f74v-9wc6

Published

Jun 19, 2020

Updated

Apr 10, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

5 known

EPSS Exploitation Probability

via FIRST.org ↗

90.1%probability of exploitation in next 30 days

Very High Risk100th percentile0.00%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Blast Radius

2 pkgs affected

💎activesupport💎activesupport

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.

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.

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
💎RubyGems	`activesupport`	≥ 5.0.0&&< 5.2.4.3	5.2.4.3
💎RubyGems	`activesupport`	≥ 6.0.0&&< 6.0.3.1	6.0.3.1

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

A deserialization of untrusted data vulnernerability exists in rails < 5…

hackerone.comNVDOct 2020

A deserialization of untrusted data vulnernerability exists in rails < 5…

github.comGithubMay 2020

A deserialization of untrusted data vulnernerability exists in rails < 5…

github.comGithubJan 2021

Frequently Asked Questions

O3 Security · Impact-Aware SCA

Is CVE-2020-8165 in your stack?

O3 detects CVE-2020-8165 across RubyGems dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my stack How O3 SCA works

CVSS Score

9.8/10

CVSS v3 base score

Vector breakdown

AV:Attack Vector

Network

AC:Attack Complexity

Low

PR:Privileges Required

None

UI:User Interaction