Hi Everyone, How you all doing. Recently, while assessing the security of HuliaHub(Pseudonym of a private bbp), I found a critical CR/LF vulnerability. This marks my second CR/LF injection vulnerability found in this particular program within a month, highlighting the importance of rigorous security testing and patching.

Understanding CR/LF (Carriage Return/Line Feed) Injection

CR/LF (Carriage Return/Line Feed) injection is a type of security vulnerability. CR/LF refers to a sequence of two ASCII control characters: Carriage Return (CR, ASCII code 13) and Line Feed (LF, ASCII code 10). CR/LF injection vulnerabilities occur when attackers insert CR/LF characters into input fields, parameters, file extensions or file uploads to manipulate application behavior. This can lead to exploits such as altering headers, injecting malicious code, or manipulating file content.

Discovery of the Vulnerability

The CR/LF vulnerability found in HuliaHub's authentication mechanism allows attackers to manipulate the redirect URL parameter during user authentication. This manipulation involves injecting special characters (%0D%0A), commonly used to denote new lines in HTTP headers. This vulnerability enables attackers to perform malicious actions post-authentication.

Reconnaissance and Testing

The discovery of this vulnerability began with the use of recon tools Sudomy, which helped uncover an interesting URL: https://auth.huliahub.com/onboard/userprofile/update?name=csd&organization=csd&jobtitle=csd&redirecturl=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3D9soe36Hqq3Y. This previously unnoticed endpoint sparked further investigation, leading to the identification of the CR/LF injection vulnerability.

Technical Details

The vulnerability exploits the redirect URL parameter used in HuliaHub's authentication flow. By appending %0D%0AClear-Site-Data:%22cookies%22 to the redirect URL, attackers can inject a directive that clears the user's session cookies upon redirection. This action effectively logs the user out of their HuliaHub account without their knowledge or consent.

Additionally, attackers can include %0D%0ALocation:https://evil.com or other payloads in the redirect URL, redirecting the user to a malicious website. This poses severe risks, including potential phishing attacks and unauthorized access to sensitive information.

Steps to Reproduce

• Attacker crafts a malicious URL with CR/LF injections:

https://auth.huliahub.com/onboard/userprofile/update?name=csd&organization=csd&jobtitle=csd&redirecturl=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3D9soe36Hqq3Y%0AClear-Site-Data%3A%22cookies%22%0A&ext=y

• Attacker shares the crafted URL, claiming it redirects to a legitimate site (e.g., YouTube).
• Victim accesses the URL and proceeds with the authentication process on HuliaHub.
• Upon redirection, the victim's session cookies are cleared, logging them out of HuliaHub.

• Alternatively, using another crafted URL:

https://auth.huliahub.com/onboard/userprofile/update?name=csd&organization=csd&jobtitle=csd&redirecturl=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3D9soe36Hqq3Y%0ALocation%3Ahttps://evil.com%0A&ext=y

• The victim is redirected to the specified malicious site (e.g., evil.com) after completing the authentication step.

Potential Exploits:

Apart from forced logout and redirected, attackers can exploit this vulnerability to manipulate and set cookies of other users. By injecting payloads such as %0ASet-Cookie%3A+crlfinjection%3D+value+ , or for xss /%3f%0d%0aLocation:%0d%0aContent-Type:text/html%0d%0aX-XSS-Protection%3a0%0d%0a%0d%0a%3Cscript%3Ealert%28document.domain%29%3C/script%3E ``

they can hijack sessions, gain unauthorized access, or execute other malicious activities.

Resolution and Bounty Award

Upon responsibly disclosing this vulnerability to HuliaHub, immediate actions were taken to investigate and subsequently patch the issue. Despite initial challenges in reproducing the issue, the severity of the vulnerability prompted an emergency patch to mitigate the risk promptly.

HuliaHub acknowledged the severity of the issue and recognized the importance of the report by awarding a bounty of $1,500 for the discovery and responsible disclosure of this critical security flaw.

Takeaway

Always conduct thorough reconnaissance to uncover hidden or untouched URLs and paths during security testing. These often serve as entry points for discovering critical vulnerabilities that might otherwise remain undetected.

By leveraging recon tools like Sudomy, cybersecurity researchers can expand their testing scope and uncover vulnerabilities that enhance the overall security posture of digital platforms.

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