CVE-2025-48865
CVE-2025-48865
Weakness (CWE)
CVSS Vector
v3.1- Attack Vector
- Network
- Attack Complexity
- Low
- Privileges Required
- None
- User Interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- None
Description
Fabio is an HTTP(S) and TCP router for deploying applications managed by consul. Prior to version 1.6.6, Fabio allows clients to remove X-Forwarded headers (except X-Forwarded-For) due to a vulnerability in how it processes hop-by-hop headers. Fabio adds HTTP headers like X-Forwarded-Host and X-Forwarded-Port when routing requests to backend applications. Since the receiving application should trust these headers, allowing HTTP clients to remove or modify them creates potential security vulnerabilities. Some of these custom headers can be removed and, in certain cases, manipulated. The attack relies on the behavior that headers can be defined as hop-by-hop via the HTTP Connection header. This issue has been patched in version 1.6.6.
Comprehensive Technical Analysis of CVE-2025-48865
1. Vulnerability Assessment and Severity Evaluation
CVE ID: CVE-2025-48865
CVSS Score: 9.1
Severity: Critical
Description: Fabio, an HTTP(S) and TCP router managed by Consul, has a vulnerability in versions prior to 1.6.6 that allows clients to remove or manipulate X-Forwarded headers (except X-Forwarded-For). This vulnerability arises from how Fabio processes hop-by-hop headers, which can be defined via the HTTP Connection header. The issue has been addressed in version 1.6.6.
CVSS Breakdown:
- Attack Vector (AV): Network
- Attack Complexity (AC): Low
- Privileges Required (PR): None
- User Interaction (UI): None
- Scope (S): Unchanged
- Confidentiality (C): High
- Integrity (I): High
- Availability (A): High
The high CVSS score indicates a critical vulnerability that can be exploited over the network with low complexity, requiring no user interaction or special privileges. The impact on confidentiality, integrity, and availability is significant.
2. Potential Attack Vectors and Exploitation Methods
Attack Vectors:
- Header Manipulation: An attacker can send crafted HTTP requests to remove or modify X-Forwarded headers, which are trusted by backend applications.
- MitM Attacks: Man-in-the-middle attacks can exploit this vulnerability to intercept and modify headers, leading to unauthorized access or data manipulation.
- Request Forgery: Attackers can forge requests to backend applications by manipulating headers, potentially leading to unauthorized actions or data breaches.
Exploitation Methods:
- Header Removal: By including specific headers in the HTTP Connection header, an attacker can remove X-Forwarded headers.
- Header Modification: Attackers can modify headers to inject malicious data or mislead backend applications about the origin of the request.
3. Affected Systems and Software Versions
Affected Software:
- Fabio versions prior to 1.6.6
Affected Systems:
- Any system or application that relies on Fabio for HTTP(S) and TCP routing, especially those that trust X-Forwarded headers for decision-making processes.
4. Recommended Mitigation Strategies
Immediate Actions:
- Upgrade: Upgrade Fabio to version 1.6.6 or later, which includes the patch for this vulnerability.
- Monitoring: Implement monitoring and logging to detect any unusual header manipulation or removal attempts.
Long-Term Strategies:
- Header Validation: Implement additional validation and sanitization of headers in backend applications to ensure they are not easily manipulated.
- Network Security: Enhance network security measures to detect and prevent MitM attacks.
- Regular Audits: Conduct regular security audits and vulnerability assessments to identify and mitigate similar issues.
5. Impact on Cybersecurity Landscape
Immediate Impact:
- Data Integrity: Compromised data integrity due to header manipulation can lead to incorrect decision-making and potential data breaches.
- Unauthorized Access: Manipulated headers can result in unauthorized access to sensitive information or systems.
Long-Term Impact:
- Trust Erosion: Erosion of trust in HTTP headers can lead to a reevaluation of how headers are used and trusted in web applications.
- Increased Awareness: Increased awareness of header manipulation vulnerabilities, leading to more robust security practices.
6. Technical Details for Security Professionals
Vulnerability Details:
- Root Cause: The vulnerability stems from how Fabio processes hop-by-hop headers, allowing clients to define headers as hop-by-hop via the HTTP Connection header.
- Exploit Mechanism: By including headers like X-Forwarded-Host and X-Forwarded-Port in the Connection header, an attacker can remove or modify these headers.
Patch Information:
- Patch Version: 1.6.6
- Patch Details: The patch ensures that X-Forwarded headers are not removed or modified based on the Connection header, maintaining the integrity of these headers.
References:
Conclusion: CVE-2025-48865 represents a critical vulnerability in Fabio that can be exploited to manipulate HTTP headers, leading to significant security risks. Upgrading to the patched version and implementing robust header validation are essential mitigation strategies. This vulnerability underscores the importance of careful handling and validation of HTTP headers in web applications.