CVE-2025-5318 in libssh
Summary
by MITRE • 06/24/2025
A flaw was found in the libssh library in versions less than 0.11.2. An out-of-bounds read can be triggered in the sftp_handle function due to an incorrect comparison check that permits the function to access memory beyond the valid handle list and to return an invalid pointer, which is used in further processing. This vulnerability allows an authenticated remote attacker to potentially read unintended memory regions, exposing sensitive information or affect service behavior.
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Analysis
by VulDB Data Team • 01/25/2026
The vulnerability identified as CVE-2025-5318 represents a critical out-of-bounds read flaw within the libssh library ecosystem affecting versions prior to 0.11.2. This issue resides within the sftp_handle function where improper boundary validation allows memory access beyond allocated buffers. The flaw stems from an incorrect comparison check that fails to properly validate array indices against valid handle list boundaries, creating a pathway for unauthorized memory traversal.
The technical implementation of this vulnerability manifests through a specific code path where the sftp_handle function processes SFTP (Secure File Transfer Protocol) operations without adequate bounds checking. When an authenticated remote attacker submits malicious SFTP requests, the function's flawed comparison logic permits access to memory locations beyond the legitimate handle list boundaries. This incorrect validation allows the function to return invalid pointers that subsequently get processed by downstream components, creating potential information disclosure and service disruption scenarios.
From an operational perspective, this vulnerability presents significant risks to systems relying on libssh for secure communications and file transfers. The authenticated nature of the attack means that an adversary must first establish valid credentials, but once inside the system, they can leverage this flaw to read sensitive memory regions that may contain cryptographic keys, session tokens, or other confidential data. The impact extends beyond simple information disclosure as the invalid pointer dereference could potentially cause service instability or denial of service conditions, affecting the availability of critical file transfer services.
The vulnerability aligns with CWE-129, which addresses improper validation of array index bounds, and demonstrates characteristics consistent with ATT&CK technique T1566.001 for credential harvesting through network protocols. Organizations utilizing libssh in production environments face heightened risk as this flaw could be exploited by threat actors to gain unauthorized access to sensitive information stored in memory or to disrupt critical file transfer operations. The vulnerability's remote exploitability through authenticated sessions means that even properly configured firewalls and network segmentation may not prevent its exploitation, as the attack vector operates within legitimate protocol boundaries.
Mitigation strategies should prioritize immediate patching of libssh installations to version 0.11.2 or later, which contains the necessary bounds checking fixes. Network administrators should implement monitoring for unusual SFTP activity patterns that might indicate exploitation attempts, while also reviewing authentication mechanisms to ensure that only authorized users can access the affected services. Additionally, organizations should consider implementing memory protection mechanisms such as stack canaries and address space layout randomization to reduce the effectiveness of potential exploitation attempts, though these measures do not eliminate the underlying vulnerability.