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CVE-2020-5247

HTTP Response Splitting in Puma

HIGH
7.5
CVSS Score
Published: February 28, 2020 at 04:55 PM UTC
Updated: June 17, 2026 at 03:21 AM UTC
4 products affected across 4 vendorsDebian LinuxFedoraRuby

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Severity
HIGH7.5
Exploit prediction
EPSS 3%

Description

In Puma (RubyGem) before 4.3.2 and before 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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Debian Linux· Debiandrupal
95%
9.0
Fedora· Fedora Projectrpm
95%
303132
Puma· Pumarubygems
95%
v ≤ 3.12.3v < 3.12.3v < 4.3.24.0.0 ≤ v ≤ 4.3.2
Affected range stops below 3.12.3, so it looks safe — our inference, not a vendor statement
Affected range stops below 4.3.2, so it looks safe — our inference, not a vendor statement
Ruby· Ruby Langrubygems
95%
v ≤ 2.3.02.4.0 ≤ v ≤ 2.4.72.5.0 ≤ v ≤ 2.5.62.6.0 ≤ v ≤ 2.6.42.7.0 preview1

References (7)

x_refsource_CONFIRMx_refsource_MISCMitigationThird Party Advisory
Source: [email protected]
https://github.com/puma/puma/security/advisories/GHSA-84j7-475p-hp8v
Mailing Listx_refsource_MLISTThird Party Advisory
Source: [email protected]
https://lists.debian.org/debian-lts-announce/2022/05/msg00034.html
Vendor Advisoryx_refsource_FEDORA
Source: [email protected]
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BMJ3CGZ3DLBJ5WUUKMI5ZFXFJQMXJZIK/
Vendor Advisoryx_refsource_FEDORA
Source: [email protected]
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/DIHVO3CQMU7BZC7FCTSRJ33YDNS3GFPK/
Vendor Advisoryx_refsource_FEDORA
Source: [email protected]
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/NJ3LL5F5QADB6LM46GXZETREAKZMQNRD/
x_refsource_MISCThird Party Advisory
Source: [email protected]
https://owasp.org/www-community/attacks/HTTP_Response_Splitting
x_refsource_MISCVendor Advisory
Source: [email protected]
https://www.ruby-lang.org/en/news/2019/10/01/http-response-splitting-in-webrick-cve-2019-16254

CVSS

7.5HIGH[email protected]
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
HIGH
Availability
NONE
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-113CWE-74

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