title: HTTP Response Splitting (Early Hints) in Puma
description: In Puma (RubyGem) before 4.3.3 and 3.12.4, if an application using Puma allows untrusted input in an early-hints header, an attacker can use a carriage return character to end the header and inject malicious content, such as additional headers or an entirely new response body. This vulnerability is known as HTTP Response Splitting. While not an attack in itself, response splitting is a vector for several other attacks, such as cross-site scripting (XSS). This is related to CVE-2020-5247, which fixed this vulnerability but only for regular responses. This has been fixed in 4.3.3 and 3.12.4.
problem types: CWE-113: Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Response Splitting')
affected:
{
product: Puma
vendor: puma
versions:
status: affected, version: < 3.12.4
status: affected, version: >= 4.0.0, < 4.3.3
}
metrics:
cvssV3_1: [
attackComplexity: LOW
attackVector: NETWORK
availabilityImpact: LOW
baseScore: 6.5
baseSeverity: MEDIUM
confidentialityImpact: LOW
integrityImpact: LOW
privilegesRequired: LOW
scope: CHANGED
userInteraction: REQUIRED
vectorString: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:L
version: 3.1
]