CVE-2011-4607 in PuTTY
Summary
by MITRE
PuTTY 0.59 through 0.61 does not clear sensitive process memory when managing user replies that occur during keyboard-interactive authentication, which might allow local users to read login passwords by obtaining access to the process memory.
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Analysis
by VulDB Data Team • 01/05/2025
The vulnerability identified as CVE-2011-4607 affects PuTTY versions 0.59 through 0.61 and represents a critical memory management flaw during keyboard-interactive authentication processes. This issue stems from insufficient memory clearing mechanisms within the authentication handling code, creating persistent exposure of sensitive data in process memory. The vulnerability specifically targets the authentication flow where users provide interactive responses, leaving credential information accessible to local attackers who can potentially access the process memory through various exploitation techniques.
The technical flaw manifests in the improper handling of sensitive data within PuTTY's authentication subsystem where password values and other credential information remain in memory after the authentication process completes. This memory retention occurs during the keyboard-interactive authentication phase, which typically involves multiple rounds of user input and server challenges. The failure to properly clear memory regions containing authentication credentials creates a persistent exposure window where malicious processes or attackers with local access can extract this sensitive information from the process heap or memory segments.
From an operational perspective, this vulnerability presents significant security risks for systems relying on PuTTY for remote access connections. Local users with access to the system can exploit this weakness to extract login credentials from running PuTTY processes, potentially compromising multiple accounts if the same credentials are reused across different sessions. The impact extends beyond individual authentication sessions to encompass potential credential compromise across multiple systems where PuTTY is utilized for administrative access. This vulnerability particularly affects environments where multiple users share the same system or where privilege escalation attacks are possible, as attackers can leverage this memory exposure to gather credentials for further exploitation.
The vulnerability aligns with CWE-119, which addresses improper access to memory locations, and represents a specific instance of insufficient memory clearing during authentication processes. From an attack framework perspective, this vulnerability maps to techniques described in the ATT&CK framework under credential access and privilege escalation categories, specifically targeting the collection of credentials through memory scraping methods. The attack surface is particularly broad given PuTTY's widespread use in enterprise environments for ssh connections, making this vulnerability a significant concern for security administrators. The impact is amplified by the fact that the vulnerability exists in multiple versions of PuTTY, requiring comprehensive patching across affected systems.
Mitigation strategies should prioritize immediate patching of affected PuTTY versions to the latest stable releases that address the memory clearing deficiencies. System administrators should implement monitoring solutions to detect unauthorized access attempts to process memory and establish proper access controls to limit local user privileges. Additionally, organizations should consider implementing multi-factor authentication mechanisms to reduce the impact of credential compromise, as well as conducting regular security assessments to identify similar memory management vulnerabilities in other authentication systems. The vulnerability underscores the importance of proper memory management practices in security-sensitive applications and highlights the need for thorough testing of authentication flows to prevent similar issues in other software components.