PatchSiren cyber security CVE debrief

CVE-2024-50151 Siemens CVE debrief

A slab-out-of-bounds write vulnerability exists in the Linux kernel's SMB client (CIFS) when handling encrypted SMB2 IOCTL requests. The flaw occurs in smb2_set_next_command() during request buffer consolidation for encryption. SMB2_ioctl_init() allocates a 448-byte buffer for the SMB2_IOCTL request; when a user provides an input buffer exceeding 328 bytes, the subsequent buffer squashing operation writes past the allocated memory boundary. This vulnerability is triggered when using SMB encryption, either server-enforced or via the 'seal' mount option. The KASAN-detected write of 4,116 bytes demonstrates significant memory corruption potential. Siemens has confirmed this affects the GNU/Linux subsystem of SIMATIC S7-1500 TM MFP industrial control devices, with no patch currently available.

Vendor: Siemens
Product: SIMATIC S7-1500 TM MFP - GNU/Linux subsystem
CVSS: HIGH 7.8
CISA KEV: Not listed in stored evidence
Original CVE published: 2024-04-09
Original CVE updated: 2026-05-14
Advisory published: 2024-04-09
Advisory updated: 2026-05-14

Who should care

Organizations running Siemens SIMATIC S7-1500 TM MFP with the GNU/Linux subsystem enabled, particularly those using SMB/CIFS mounts with encryption. Industrial operators with CIFS-dependent workflows and limited patch availability should prioritize access controls.

Technical summary

The vulnerability stems from insufficient buffer size validation in the SMB2 client implementation. When smb2_ioctl_init() allocates a 448-byte request buffer and smb2_set_next_command() consolidates buffers for encryption, input buffers larger than 328 bytes cause a write beyond the allocated slab memory. The KASAN report shows a 4,116-byte write operation triggering the out-of-bounds access. This affects local attackers with low privileges who can mount SMB shares with encryption enabled.

Defensive priority

HIGH

Recommended defensive actions

Restrict interactive shell access to the GNU/Linux subsystem to trusted personnel only
Build and run only applications from trusted sources
Monitor for anomalous SMB client activity on affected systems
Apply kernel updates from Siemens when available
Consider network segmentation to limit SMB exposure for affected industrial devices

Evidence notes

The vulnerability was resolved in the Linux kernel per the CVE description. CISA's ICS advisory ICSA-24-102-01 (published 2024-04-09, last modified 2026-05-14) tracks this issue for Siemens industrial products. The advisory's remediation section explicitly states 'Currently no fix is available' for the affected product.

Official resources

2024-04-09