CVE-2020-8184Public exploitNetwork attack vector

Security decision bypass via percent-decoded cookie names

Published Jun 19, 2020 · Updated Aug 4, 2024

Cookie prefix forgery in Rack before 2.1.4 and 2.2.0 through 2.2.2 allows remote attackers to influence security decisions via cookies. Rack::Utils.parse_cookies_header percent-decodes cookie names and collapses an encoded name with its literal equivalent, allowing the attacker-controlled first value to win. Exploitation requires an application that trusts __Host- or __Secure- cookie prefixes and an attacker able to set arbitrary cookies sent to it; the consequence is acceptance of an insecure or cross-origin request.

CVSS severity7.5
High
EPSS probability2.94%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cookie prefix forgery in Rack before 2.1.4 and 2.2.0 through 2.2.2 allows remote attackers to influence security decisions via cookies. Rack::Utils.parse_cookies_header percent-decodes cookie names and collapses an encoded name with its literal equivalent, allowing the attacker-controlled first value to win. Exploitation requires an application that trusts __Host- or __Secure- cookie prefixes and an attacker able to set arbitrary cookies sent to it; the consequence is acceptance of an insecure or cross-origin request.

The record

CVE
CVE-2020-8184
Published
Jun 19, 2020
Updated
Aug 4, 2024
Vendor
Rack
Product
Rack
Classifications
CWE-784, CWE-20
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 19, 2020CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=rack >= 2.2.3, rack >= 2.1.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Rack · Rackversion=rack >= 2.2.3, rack >= 2.1.4

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:P/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-784Reliance on Cookies without Validation and Integrity Checking in a Security Decision
CWE-20Improper Input Validation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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