Overview
This report details the buffer overflow vulnerability in libsmb2 6.2+ identified as CVE-2025-57632. The vulnerability impacts systems running this particular software version, presenting a significant threat as it can potentially allow an attacker to execute arbitrary code, leading to system compromise or data leakage.
Vulnerability Summary
CVE ID: CVE-2025-57632
Severity: High (7.5 CVSS)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: System compromise, data leakage, memory corruption, and crashes
Affected Products
Product | Affected Versions
libsmb2 | 6.2+
How the Exploit Works
The vulnerability stems from improper handling and validation of SMB2 chained PDUs inside libsmb2. When processing these chained PDUs, the software repeatedly calls the function smb2_add_iovector() to append to a fixed-size iovec array without checking the upper bound, v->niov, which is capped at 256 (SMB2_MAX_VECTORS).
An attacker can exploit this vulnerability by crafting responses with numerous chained PDUs, causing an overflow of v->niov. This results in heap out-of-bounds writes, which lead to memory corruption, system crashes, and potentially arbitrary code execution. Furthermore, the SMB2_OPLOCK_BREAK path bypasses message ID validation, making it easier for an attacker to exploit this vulnerability.
Conceptual Example Code
Below is a conceptual example of how an attacker might exploit this vulnerability. This pseudocode represents a malicious SMB2 response with an abnormal number of chained PDUs:
SMB2_Header {
ProtocolId: SMB2,
MessageId: 0x1,
...
}
SMB2_Chained_PDU {
NextCommand: 0x1,
...
}
...
SMB2_Chained_PDU {
NextCommand: 0x100, // Exceeds SMB2_MAX_VECTORS
...
}This code results in an overflow of the v->niov variable, leading to memory corruption and potential arbitrary code execution. By sending a large number of these responses, an attacker can crash the system or even take control of it.
