CVE-2004-2486 in Dropbear SSH Server
Summary
by MITRE
The DSS verification code in Dropbear SSH Server before 0.43 frees uninitialized variables, which might allow remote attackers to gain access.
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Analysis
by VulDB Data Team • 07/05/2025
The vulnerability identified as CVE-2004-2486 represents a critical security flaw in the Dropbear SSH server implementation that existed prior to version 0.43. This issue resides within the Digital Signature Standard verification code component, which is fundamental to the secure authentication mechanisms of the SSH protocol. The vulnerability stems from improper memory management practices where the system fails to initialize certain variables before their use in cryptographic verification operations. This particular flaw demonstrates a classic example of uninitialized variable usage that can lead to unpredictable behavior and potential security exploits.
The technical nature of this vulnerability places it squarely within the realm of memory safety issues and can be classified under CWE-457 as "Use of Uninitialized Variable." The flaw manifests when the DSS verification process attempts to validate digital signatures without properly initializing memory locations that contain critical cryptographic parameters. This uninitialized state creates a scenario where attackers can potentially manipulate the verification process by exploiting the unpredictable values that may reside in these memory locations. The remote attack vector means that malicious actors can leverage this weakness from outside the local network, making it particularly dangerous for systems exposed to the internet.
The operational impact of this vulnerability extends beyond simple authentication failures and can potentially allow remote attackers to bypass the entire SSH authentication mechanism. When uninitialized variables are used in cryptographic operations, the verification process becomes unreliable and susceptible to manipulation. Attackers could potentially craft specially crafted signatures or exploit the uninitialized memory to bypass authentication checks entirely, effectively gaining unauthorized access to systems running vulnerable versions of Dropbear SSH. This represents a severe privilege escalation vulnerability that undermines the fundamental security model of SSH communications.
Mitigation strategies for CVE-2004-2486 require immediate deployment of patches to update Dropbear SSH servers to version 0.43 or later, which contains the necessary fixes for proper variable initialization. System administrators should conduct comprehensive inventory checks to identify all instances of vulnerable Dropbear installations across their network infrastructure. The remediation process should also include implementing network segmentation and access controls to limit exposure of SSH services to untrusted networks. Additionally, organizations should consider implementing intrusion detection systems to monitor for suspicious authentication attempts that might indicate exploitation attempts against this vulnerability. This vulnerability aligns with several ATT&CK techniques including T1021.004 for SSH and T1566 for credential access, making comprehensive monitoring and defense strategies essential for protecting against potential exploitation attempts.