CVE-2020-29652 in SSH Component
Summary
by MITRE • 12/17/2020
A nil pointer dereference in the golang.org/x/crypto/ssh component through v0.0.0-20201203163018-be400aefbc4c for Go allows remote attackers to cause a denial of service against SSH servers.
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Analysis
by VulDB Data Team • 07/03/2026
The vulnerability under discussion represents a critical nil pointer dereference flaw within the golang.org/x/crypto/ssh package, specifically affecting versions up to v0.0.0-20201203163018-be400aefbc4c. This issue resides in the go programming language ecosystem and impacts SSH server implementations that utilize this cryptographic library. The flaw manifests when remote attackers can manipulate input data in such a way that causes the program to attempt accessing a nil pointer reference, resulting in an unexpected termination of the service.
The technical nature of this vulnerability stems from inadequate input validation and error handling within the ssh package's internal processing mechanisms. When legitimate SSH protocol communications are received by vulnerable servers, specific sequences of packets or malformed data can trigger the nil pointer dereference condition. This occurs because the code fails to properly check for null or uninitialized pointers before attempting to access their memory locations, which is a classic software engineering error that violates fundamental defensive programming principles.
From an operational perspective, this vulnerability enables remote attackers to execute successful denial of service attacks against SSH servers running affected versions of the golang crypto/ssh library. The impact extends beyond simple service disruption as it can be exploited by attackers without requiring authentication or elevated privileges. The attack vector is particularly concerning because SSH servers are fundamental infrastructure components that provide secure remote access to systems, making this vulnerability a significant threat to network availability and operational continuity.
The vulnerability's classification aligns with CWE-476, which addresses NULL pointer dereference issues in software implementations. This weakness falls under the broader category of memory safety vulnerabilities that have been extensively documented in cybersecurity literature and contribute significantly to system instability and potential compromise. The ATT&CK framework categorizes this as a Denial of Service technique under the T1499 sub-technique, specifically targeting network services to make them unavailable to legitimate users.
Organizations utilizing Go-based SSH servers should immediately upgrade to patched versions of the golang.org/x/crypto/ssh library to remediate this vulnerability. The recommended mitigation strategy includes implementing comprehensive input validation mechanisms and thorough error handling procedures within applications that rely on this cryptographic library. Additionally, network administrators should consider implementing intrusion detection systems to monitor for suspicious SSH traffic patterns that might indicate exploitation attempts. Regular security assessments and vulnerability scanning of all infrastructure components utilizing Go libraries are essential practices to identify and address similar weaknesses before they can be exploited by malicious actors in the broader cybersecurity landscape.