CVE-2005-0467 in PuTTY
Summary
by MITRE
Multiple integer overflows in the (1) sftp_pkt_getstring and (2) fxp_readdir_recv functions in the PSFTP and PSCP clients for PuTTY 0.56, and possibly earlier versions, allow remote malicious web sites to execute arbitrary code via SFTP responses that corrupt the heap after insufficient memory has been allocated.
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Analysis
by VulDB Data Team • 03/10/2021
The vulnerability identified as CVE-2005-0467 represents a critical security flaw in the PuTTY suite of SSH client applications, specifically affecting versions 0.56 and potentially earlier releases. This issue stems from improper handling of memory allocation during SFTP protocol operations, creating conditions where malicious actors can exploit the software's response processing mechanisms to achieve arbitrary code execution on affected systems. The vulnerability impacts both PSFTP and PSCP client components, which are integral parts of the PuTTY suite used for secure file transfers and remote connections.
The technical implementation of this vulnerability involves two distinct functions within the SFTP client processing code: sftp_pkt_getstring and fxp_readdir_recv. These functions demonstrate integer overflow conditions when processing string data and directory listing responses received from SFTP servers. When these functions encounter specially crafted SFTP responses containing maliciously sized data structures, they fail to properly validate the expected memory requirements before allocation. This insufficient validation leads to heap corruption through integer overflows, where the calculated buffer sizes exceed the intended limits, causing memory allocation failures that result in unpredictable memory layout changes.
The operational impact of CVE-2005-0467 extends beyond simple code execution capabilities, as it allows remote attackers to manipulate the heap memory structures of vulnerable PuTTY clients. This heap corruption can lead to various security consequences including denial of service conditions, privilege escalation opportunities, and potential complete system compromise. Attackers can exploit this vulnerability by hosting malicious web content or controlling SFTP servers that respond with crafted data structures designed to trigger the integer overflow conditions in the affected functions. The vulnerability is particularly concerning because it can be exploited through web-based attacks without requiring user interaction beyond initiating the SFTP connection process.
From a cybersecurity framework perspective, this vulnerability aligns with CWE-190, which specifically addresses integer overflow conditions, and demonstrates characteristics consistent with ATT&CK technique T1210, involving exploitation of remote services through protocol manipulation. The vulnerability's classification as a heap-based buffer overflow indicates it operates within the broader category of memory corruption vulnerabilities that have historically been primary attack vectors for sophisticated exploitation campaigns. The fact that this affects both PSFTP and PSCP clients indicates a systemic weakness in the SFTP processing architecture that impacts multiple components within the PuTTY ecosystem.
Mitigation strategies for CVE-2005-0467 require immediate implementation of version updates to PuTTY 0.57 or later, which contain patches specifically addressing the integer overflow conditions in the affected functions. Organizations should also implement network segmentation and access controls to limit exposure to potentially malicious SFTP servers, particularly in environments where users may connect to untrusted external systems. Additionally, security monitoring should be enhanced to detect unusual SFTP connection patterns or data transfer behaviors that might indicate exploitation attempts. The vulnerability serves as a reminder of the critical importance of proper input validation and memory management in network protocol implementations, particularly in widely-used security tools where exploitation can have widespread consequences across multiple organizational domains.