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HTTP Response Splitting in Puma

Moderate severity GitHub Reviewed Published Feb 27, 2020 in puma/puma • Updated May 16, 2023

Package

bundler puma (RubyGems)

Affected versions

< 3.12.3
>= 4.0.0, < 4.3.2

Patched versions

3.12.4
4.3.3

Description

In Puma (RubyGem) before 4.3.2 and 3.12.3, if an application using Puma allows untrusted input in a response header, an attacker can use newline characters (i.e. CR, LF or/r, /n) 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-2019-16254, which fixed this vulnerability for the WEBrick Ruby web server.

This has been fixed in versions 4.3.2 and 3.12.3 by checking all headers for line endings and rejecting headers with those characters.

References

@nateberkopec nateberkopec published to puma/puma Feb 27, 2020
Reviewed Feb 28, 2020
Published to the GitHub Advisory Database Feb 28, 2020
Published by the National Vulnerability Database Feb 28, 2020
Last updated May 16, 2023

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
Low

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:L

EPSS score

0.675%
(80th percentile)

Weaknesses

CVE ID

CVE-2020-5247

GHSA ID

GHSA-84j7-475p-hp8v

Source code

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