Compliance Impact

This vulnerability allows unauthenticated attackers to impersonate any user, including administrators, and gain unauthorized access to files and user accounts. Such unauthorized access and potential data exposure can lead to violations of data protection regulations like GDPR and HIPAA, which require strict access controls and protection of personal and sensitive information.

The ability to create backdoor user accounts without authorization further increases the risk of data breaches and non-compliance with standards that mandate accountability and auditability of user actions.

Therefore, organizations using vulnerable versions of FileBrowser with proxy authentication misconfigured may fail to meet compliance requirements related to confidentiality, integrity, and access control.

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Detection Guidance

This vulnerability can be detected by checking if your FileBrowser server is configured with proxy authentication (auth.method=proxy) and is directly accessible over the network without proper firewall or network isolation.

To detect potential exploitation attempts, monitor HTTP requests for forged headers such as 'X-Remote-User' that could be used to impersonate users without credentials.

You can use network monitoring tools or commands like the following to inspect incoming HTTP headers:

• Using tcpdump to capture HTTP traffic on port 80 or 443: tcpdump -i <interface> -A 'tcp port 80 or 443 and (((ip[2:2] - ((ip[0]&0xf)<<2)) - ((tcp[12]&0xf0)>>2)) != 0)'
• Using tshark to filter HTTP headers containing 'X-Remote-User': tshark -i <interface> -Y 'http.header contains "X-Remote-User"' -T fields -e http.host -e http.request.full_uri -e http.header

Additionally, review FileBrowser logs for any unexpected user creation events or authentication bypass attempts.

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Mitigation Strategies

Immediate mitigation steps include:

• Restrict network access to the FileBrowser server by implementing strict firewall rules or network isolation to prevent direct access from untrusted networks.
• Disable or avoid using proxy authentication (auth.method=proxy) until a secure fix or update is applied.
• Apply any available patches or updates from the FileBrowser project that address this vulnerability.
• Configure the server to validate trusted proxy IP addresses to ensure that only legitimate proxies can set authentication headers.
• Make auto-user-creation an opt-in feature rather than automatic to prevent unauthorized account creation.

These steps help prevent unauthenticated attackers from impersonating users or creating backdoor accounts.

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Executive Summary

This vulnerability affects File Browser, a file management interface. When configured with proxy authentication, an unauthenticated attacker who can directly reach the server can impersonate any user, including administrators, by sending a single forged HTTP header without needing any credentials.

Additionally, if the attacker specifies a username that does not exist, the server will automatically create a new user account without any authorization, effectively allowing unauthorized account creation.

Although this issue has been known and documented in the product's documentation for several years, it had not been previously documented as a security vulnerability.

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Impact Analysis

This vulnerability can have serious impacts because it allows attackers to impersonate any user, including administrators, without credentials. This can lead to unauthorized access to sensitive files and data managed by File Browser.

Moreover, attackers can create new user accounts without authorization, potentially escalating their access or maintaining persistent unauthorized access.

The overall impact includes a high risk of data compromise and unauthorized file management actions, which can disrupt operations and lead to data breaches.

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