CVE-2020-5247: HTTP Response Splitting in Puma
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.
Other sources
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.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
rubygems/pumato a version that resolves this vulnerability.Fixed in 4.3.3 - Upgrade
Upgrade
rubygems/pumato a version that resolves this vulnerability.Fixed in 3.12.4 - Upgrade
Upgrade
puma (RubyGem)to a version that resolves this vulnerability.Fixed in 4.3.2 - Upgrade
Upgrade
puma (RubyGem)to a version that resolves this vulnerability.Fixed in 3.12.3
Event History
Frequently Asked Questions
What is CVE-2020-5247?
CVE-2020-5247 is a vulnerability in Puma (RubyGem) that allows an attacker to inject malicious content via newline characters in response headers.
What is the severity of CVE-2020-5247?
The severity of CVE-2020-5247 is high with a CVSS score of 7.5.
Which versions of Puma are affected by CVE-2020-5247?
Puma versions before 4.3.2 and before 3.12.3 are affected by CVE-2020-5247.
How can an attacker exploit CVE-2020-5247?
An attacker can exploit CVE-2020-5247 by using newline characters to end the header and inject malicious content, such as additional headers or a new response body.
Where can I find more information about CVE-2020-5247?
You can find more information about CVE-2020-5247 on the GitHub security advisory page and the OWASP website.