CVE-2005-4178 in Dropbear SSH Server
Summary
by MITRE
Buffer overflow in Dropbear server before 0.47 allows authenticated users to execute arbitrary code via unspecified inputs that cause insufficient memory to be allocated due to an incorrect expression that does not enforce the proper order of operations.
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Analysis
by VulDB Data Team • 06/28/2025
The vulnerability identified as CVE-2005-4178 represents a critical buffer overflow flaw within the Dropbear SSH server implementation prior to version 0.47. This security weakness stems from improper memory allocation handling during the processing of authenticated user inputs, creating a scenario where maliciously crafted data can trigger memory corruption. The vulnerability specifically manifests when the server processes certain inputs that result in insufficient memory allocation due to an incorrect mathematical expression that fails to enforce proper order of operations. This type of flaw falls under the common weakness enumeration CWE-121, which categorizes buffer overflow conditions that occur when insufficient memory is allocated for data processing. The Dropbear SSH server, designed as a lightweight alternative to OpenSSH, was widely adopted for embedded systems and environments where resource constraints necessitated efficient implementations. However, this particular vulnerability demonstrates how optimization efforts in memory management can inadvertently introduce security risks when proper validation and order of operations are not rigorously enforced.
The operational impact of this vulnerability extends beyond simple code execution privileges, as it enables authenticated users to potentially gain arbitrary code execution on the target system. This represents a significant escalation from typical privilege boundaries since the attacker must first establish authentication credentials before exploiting the buffer overflow. The nature of the flaw suggests that the vulnerability could be exploited through various input vectors that cause the server to miscalculate memory requirements, potentially leading to stack corruption or heap overflow conditions. Attackers could leverage this vulnerability to execute malicious code with the privileges of the Dropbear server process, which typically runs with elevated system permissions. The vulnerability's classification aligns with ATT&CK technique T1059, which covers command and script injection methods, as successful exploitation would likely involve injecting and executing arbitrary commands on the compromised system. This makes the vulnerability particularly dangerous in environments where Dropbear serves as the primary SSH server implementation and where authenticated access might be obtained through legitimate means such as compromised credentials or weak authentication mechanisms.
Mitigation strategies for CVE-2005-4178 primarily focus on immediate software updates and patch deployment to versions 0.47 and later, which contain the corrected memory allocation logic. Organizations should prioritize patching all systems running vulnerable versions of Dropbear, particularly those in critical infrastructure environments where the server handles sensitive operations. Additionally, implementing network segmentation and access controls can reduce the attack surface by limiting who can establish authenticated connections to the SSH server. The vulnerability highlights the importance of proper input validation and memory management practices in security-critical applications, emphasizing that even seemingly benign mathematical expressions can introduce significant security risks when not properly validated. System administrators should also consider implementing intrusion detection systems that monitor for unusual memory allocation patterns or potential exploitation attempts. From a defensive standpoint, this vulnerability underscores the necessity of thorough code review processes that examine not only functional correctness but also security implications of mathematical operations and memory management decisions. The remediation approach should include comprehensive testing of patched versions to ensure that the fix properly addresses the root cause without introducing regressions in functionality, as the memory allocation corrections must maintain backward compatibility while preventing the buffer overflow conditions that previously existed.