CVE-2009-2957 in dnsmasq
Summary
by MITRE
Heap-based buffer overflow in the tftp_request function in tftp.c in dnsmasq before 2.50, when --enable-tftp is used, might allow remote attackers to execute arbitrary code via a long filename in a TFTP packet, as demonstrated by a read (aka RRQ) request.
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Analysis
by VulDB Data Team • 09/28/2025
The vulnerability described in CVE-2009-2957 represents a critical heap-based buffer overflow in the dnsmasq network infrastructure software. This flaw exists within the tftp_request function located in the tftp.c file of dnsmasq versions prior to 2.50. The vulnerability specifically manifests when the software is compiled with the --enable-tftp configuration option, which enables TFTP (Trivial File Transfer Protocol) functionality. The issue occurs during processing of TFTP read requests, where an attacker can exploit a malformed filename field in the TFTP packet to trigger the buffer overflow condition.
The technical implementation of this vulnerability involves improper bounds checking within the TFTP request handling mechanism. When dnsmasq receives a TFTP read request containing an excessively long filename, the software fails to validate the length of the incoming data against the allocated buffer space. This allows an attacker to write beyond the intended memory boundaries, potentially overwriting adjacent memory locations including function return addresses, stack canaries, or other critical program state information. The heap-based nature of the overflow indicates that the vulnerable buffer is allocated on the heap rather than the stack, making exploitation more complex but still feasible for skilled attackers.
The operational impact of this vulnerability extends beyond simple code execution, as it represents a remote code execution vector that can be exploited without authentication. Attackers can leverage this flaw to gain arbitrary code execution on systems running vulnerable versions of dnsmasq, potentially leading to complete system compromise. This vulnerability is particularly dangerous in network environments where dnsmasq serves as a DHCP and DNS server, as it can be exploited by remote attackers without requiring any network credentials. The vulnerability's exploitation can result in unauthorized access to network resources, data exfiltration, or establishment of persistent backdoors within the network infrastructure.
Security professionals should note that this vulnerability aligns with CWE-121, heap-based buffer overflow, and maps to attack techniques in the MITRE ATT&CK framework under T1059.1001 for command and scripting interpreter and T1068 for exploit for privilege escalation. Organizations should immediately upgrade to dnsmasq version 2.50 or later to remediate this vulnerability, as the fix includes proper input validation and bounds checking for TFTP filename handling. Additionally, network administrators should consider implementing network segmentation and monitoring to detect unusual TFTP traffic patterns that might indicate exploitation attempts. The vulnerability demonstrates the importance of proper memory management in network services and highlights the need for regular security updates and vulnerability assessments in critical infrastructure software components.