CVE-2018-25103 in lighttpd
Summary
by MITRE • 06/17/2024
There exists a use-after-free-vulnerability in lighttpd <= 1.4.50 that can allow access to do a case-insensitive comparison against the reused pointer.
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Analysis
by VulDB Data Team • 07/10/2024
The vulnerability identified as CVE-2018-25103 represents a critical use-after-free condition within the lighttpd web server software version 1.4.50 and earlier. This type of vulnerability occurs when a program continues to reference memory that has already been freed, creating potential avenues for exploitation. The specific flaw manifests in the handling of certain HTTP requests where memory management becomes compromised, allowing attackers to manipulate the program flow through memory reuse patterns. The vulnerability specifically impacts the comparison operations within the web server's processing logic, creating opportunities for unauthorized access and potentially arbitrary code execution.
The technical implementation of this use-after-free vulnerability stems from improper memory deallocation and subsequent reuse within lighttpd's internal request processing mechanisms. When the web server handles certain HTTP requests, it allocates memory for processing headers or other request components, which are then freed upon completion of the operation. However, the program fails to properly nullify pointers or validate memory states before allowing subsequent operations to access this freed memory region. This allows an attacker to control the contents of the freed memory and potentially manipulate the comparison logic that occurs during case-insensitive string operations, where the reused pointer may contain attacker-controlled data.
The operational impact of CVE-2018-25103 extends beyond simple memory corruption, as it can enable attackers to perform case-insensitive comparisons against memory that has already been freed and potentially repurposed. This creates opportunities for attackers to manipulate the comparison outcomes in ways that could bypass security checks or redirect program execution. The vulnerability particularly affects web server configurations that process user-supplied input through HTTP headers or request parameters, where the attacker-controlled data could influence the comparison logic. This type of vulnerability aligns with CWE-416, which specifically addresses use-after-free conditions, and represents a significant risk to web server security and data integrity.
Mitigation strategies for CVE-2018-25103 primarily focus on immediate software updates to versions that have addressed this memory management flaw. System administrators should prioritize upgrading lighttpd to version 1.4.51 or later, which includes proper memory deallocation and pointer validation mechanisms. Additionally, implementing proper input validation and sanitization measures can help reduce the attack surface by limiting the amount of user-controllable data that reaches the vulnerable code paths. Network-level protections such as intrusion detection systems and web application firewalls can provide additional layers of defense by monitoring for suspicious request patterns that might indicate exploitation attempts. The vulnerability also aligns with ATT&CK technique T1059, which involves command and scripting interpreter usage, as exploitation could enable attackers to execute arbitrary commands on the affected system. Organizations should also consider implementing memory protection mechanisms such as stack canaries and address space layout randomization to make exploitation more difficult and detect potential attacks through abnormal memory access patterns.