An issue was discovered in Ruby through 2.5.8, 2.6.x through 2.6.6, and 2.7.x through 2.7.1. WEBrick, a simple HTTP server bundled with Ruby, had not checked the transfer-encoding header value rigorously. An attacker may potentially exploit this issue to bypass a reverse proxy (which also has a poor header check), which may lead to an HTTP Request Smuggling attack.
https://github.com/ruby/webrick/commit/8946bb38b4d87549f0d99ed73c62c41933f97cc7
https://hackerone.com/reports/965267
https://www.ruby-lang.org/en/news/2020/09/29/http-request-smuggling-cve-2020-25613/
Source: MITRE
Published: 2020-10-06
Updated: 2022-01-01
Type: CWE-444
Base Score: 5
Vector: AV:N/AC:L/Au:N/C:N/I:P/A:N
Impact Score: 2.9
Exploitability Score: 10
Severity: MEDIUM
Base Score: 7.5
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Impact Score: 3.6
Exploitability Score: 3.9
Severity: HIGH