CVE-2026-59293 in Spring Integration
Summary
by MITRE • 08/27/2026
Unless the application explicitly raises smbMinVersion, the jCIFS client will negotiate down to SMB1/CIFS, which lacks mandatory signing/encryption and is vulnerable to NTLM relay and content-tampering MITM. Spring Integration 7.1.0 Spring Integration 7.0.0 - 7.0.5 Spring Integration 6.5.0 - 6.5.10 Spring Integration 6.4.0 - 6.4.12
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Analysis
by VulDB Data Team • 08/27/2026
The vulnerability described pertains to the default behavior of the jCIFS library when used within Spring Integration applications, specifically affecting versions such as Spring Integration 7.1.0 and earlier releases in the 7.0.x, 6.5.x, and 6.4.x series. The core issue stems from a lack of explicit configuration for minimum SMB protocol version requirements. By default, if an application does not explicitly set the smbMinVersion parameter to enforce a higher security standard, the jCIFS client will automatically negotiate down to Server Message Block version 1 (SMB1), also known as CIFS. This automatic downgrade is driven by backward compatibility considerations but introduces significant security risks because SMB1 was designed in an era where network trust assumptions were far more relaxed than they are today.
The technical flaw lies in the protocol negotiation phase of the SMB connection establishment process. When jCIFS initiates a session with a remote server, it sends a list of supported dialects. If the smbMinVersion is not configured to exclude older protocols, the client includes SMB1 in its acceptable options. Many legacy servers still support SMB1 for compatibility reasons and may prefer or default to this protocol if offered by the client. Consequently, even if both parties could technically communicate over more secure versions like SMB2 or SMB3, the connection defaults to the weakest common denominator. This behavior effectively bypasses modern security controls that are only available in newer protocol versions.
The operational impact of utilizing SMB1 is severe due to its architectural weaknesses regarding authentication and data integrity. SMB1 does not mandate message signing or encryption by default. Message signing ensures that packets cannot be altered in transit without detection, while encryption protects the confidentiality of the data being transferred. Without these protections, an attacker positioned on the network path can perform a Man-in-the-Middle (MITM) attack with relative ease. The most critical risk associated with this configuration is NTLM relay attacks. In such scenarios, an attacker intercepts the SMB1 authentication traffic and relays it to another service or server that accepts NTLM hashes for authentication. This allows the attacker to impersonate the legitimate user without ever needing to crack their password hash, effectively gaining unauthorized access to resources protected by those credentials.
Furthermore, because SMB1 lacks mandatory encryption, any data transmitted over this connection is visible in plaintext to network sniffers. An adversary can capture sensitive files, commands, or configuration details simply by monitoring traffic on the same subnet. The lack of content integrity checks means that an attacker could also tamper with file contents during transfer, leading to potential data corruption or injection attacks if the receiving application processes unverified inputs derived from these SMB shares. This combination of authentication bypass and data exposure creates a high-severity risk profile for any enterprise environment relying on this default configuration.
From a classification perspective, this vulnerability aligns closely with CWE-326, which denotes Inadequate Encryption Strength, as the connection fails to use strong cryptographic protections by default. It also relates to CWE-757: Selection of Less-Secure Algorithm During Negotiation, highlighting the failure to enforce a secure protocol version during the handshake process. In terms of offensive security tactics, this scenario maps directly to MITRE ATT&CK technique T1557.002, known as Adversary-in-the-Middle or LLMNR/NBT-NS Poisoning and SMB Relay Attacks. The exploitation path typically involves passive listening for authentication requests followed by active relay attempts against vulnerable services that accept NTLMv1 or weak NTLMv2 responses over unsecured channels.
To mitigate this vulnerability, organizations must explicitly configure the jCIFS client to enforce a minimum protocol version of at least SMB2.0 or preferably SMB3.x. This is achieved by setting the smbMinVersion property in the application configuration files or through programmatic initialization before any network connections are established. By raising this threshold, the client will refuse to negotiate with servers that only support SMB1, thereby forcing a connection over a protocol version that supports mandatory signing and optional encryption. Additionally, administrators should audit their infrastructure for legacy systems still relying on SMB1 and upgrade them where possible, as disabling SMB1 at the operating system level provides an additional layer of defense-in-depth. Regular security assessments and penetration testing focused on network authentication flows can help identify instances where this misconfiguration persists in production environments.