What’s Vulnerable › Vulnerabilities

CVE-2020-8184: Rack allows Percent-encoded cookies to overwrite existing prefixed cookie names

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 2.9% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2020-06-19 · updated 2026-06-17
• Weakness: CWE-784

Description

A reliance on cookies without validation/integrity check security vulnerability exists in rack < 2.2.3, rack < 2.1.4 that makes it is possible for an attacker to forge a secure or host-only cookie prefix.

Affected products

• Canonical Ubuntu Linux: 18.04
• Debian Linux: 9.0, 10.0
• Rack Project Rack: before 2.1.4; from 2.2.0 before 2.2.3 — fixed in 2.1.4, 2.2.3
• Rubygems Rack: before 2.1.4; from 2.2.0 before 2.2.3; 0.1.0, 0.2.0, 0.3.0, 0.4.0, 0.9.0, 0.9.1 (+86) — fixed in 2.1.4, 2.2.3

How to fix

Upgrade to a fixed version: Rack Project Rack 2.1.4, 2.2.3; Rubygems Rack 2.1.4, 2.2.3. Check the vendor advisory for mitigations.

References

• https://groups.google.com/g/rubyonrails-security/c/OWtmozPH9Ak
• https://hackerone.com/reports/895727
• https://lists.debian.org/debian-lts-announce/2020/07/msg00006.html
• https://lists.debian.org/debian-lts-announce/2023/01/msg00038.html
• https://usn.ubuntu.com/4561-1/
• https://groups.google.com/g/rubyonrails-security/c/OWtmozPH9Ak
• https://hackerone.com/reports/895727
• https://lists.debian.org/debian-lts-announce/2020/07/msg00006.html
• https://lists.debian.org/debian-lts-announce/2023/01/msg00038.html
• https://usn.ubuntu.com/4561-1/

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