CVE-2025-57632 is a buffer overflow vulnerability identified in libsmb2 version 6.2 and above, a library used for SMB2 protocol communication. The vulnerability occurs during the processing of SMB2 chained Protocol Data Units (PDUs), specifically when libsmb2 repeatedly calls the function smb2_add_iovector() to append data to a fixed-size iovec array. The array has a maximum size defined by SMB2_MAX_VECTORS (256 entries), but libsmb2 fails to check if the number of appended vectors (v->niov) exceeds this limit. An attacker can exploit this by crafting malicious SMB2 responses containing a large number of chained PDUs, causing an overflow of the iovec array. This overflow leads to heap out-of-bounds writes, resulting in memory corruption that can crash the application or enable arbitrary code execution. Notably, the SMB2_OPLOCK_BREAK code path bypasses message ID validation, which normally helps prevent replay or injection attacks, thereby increasing the risk of exploitation. The vulnerability requires no authentication or user interaction and can be triggered remotely over the network. Although no public exploits have been reported yet and no patches are currently available, the vulnerability poses a significant risk to systems using libsmb2 for SMB2 communication, including client and server implementations in various operating systems and networked devices. The CVSS v3.1 score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) indicates a high severity primarily due to the impact on availability and ease of remote exploitation without privileges or user interaction.

For European organizations, this vulnerability presents a serious risk to the availability and stability of SMB2-based file sharing and network communication services. Exploitation can lead to application crashes and potential arbitrary code execution, which could be leveraged for further network compromise or denial of service attacks. Organizations relying on libsmb2 in critical infrastructure, enterprise file servers, or network appliances may experience service disruptions. Although confidentiality and integrity impacts are not directly indicated, the possibility of arbitrary code execution could allow attackers to escalate privileges or move laterally within networks. The lack of authentication requirements and remote exploitability increase the threat surface, especially in environments exposing SMB2 services to untrusted networks. European entities with extensive SMB2 deployments, including government agencies, financial institutions, and large enterprises, face heightened risk. The absence of patches necessitates immediate risk mitigation to prevent exploitation. Additionally, the SMB2_OPLOCK_BREAK path bypassing message ID validation may facilitate more sophisticated attacks, increasing potential impact.

1. Immediately audit and inventory all systems and devices using libsmb2 version 6.2 or later to identify vulnerable instances. 2. Restrict SMB2 traffic exposure by implementing network segmentation and firewall rules to limit access to SMB2 services only to trusted internal networks. 3. Monitor network traffic for abnormal SMB2 chained PDU patterns or unusually large numbers of chained PDUs that could indicate exploitation attempts. 4. Employ intrusion detection/prevention systems (IDS/IPS) with updated signatures or heuristics to detect malformed SMB2 packets targeting this vulnerability. 5. Disable or limit SMB2 protocol usage on endpoints and servers where feasible, or enforce SMB signing and encryption to reduce attack surface. 6. Engage with vendors and open-source communities for timely patches or workarounds; apply updates promptly once available. 7. Consider deploying application-level sandboxing or process isolation for services using libsmb2 to contain potential crashes or code execution. 8. Educate network and security teams about this vulnerability to enhance incident response readiness. 9. For critical systems, implement additional monitoring of process crashes and memory anomalies related to libsmb2 components.