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GHSA-33vf-4xgg-9r58

MediumCVSS 6.5 / 10
Published Mar 3, 2020·Last modified Feb 4, 2026
Affected Components(0)

No affected components available

Description

Impact

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.

Patches

This has been fixed in 4.3.3 and 3.12.4.

Workarounds

Users can not allow untrusted/user input in the Early Hints response header.

For more information

If you have any questions or comments about this advisory:

Risk Scores
Base Score
6.5

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. The attacker needs the user to perform some action, like clicking a link. The vulnerability can affect other systems as well, not just the initial system. There is a low impact on the confidentiality of the information. There is a low impact on the integrity of the data. There is a low impact on the availability of the system.

Threat Intelligence
6.0

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
1.57%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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