PatchSiren cyber security CVE debrief

CVE-2025-21683 Siemens CVE debrief

A memory leak vulnerability exists in the Linux kernel's BPF subsystem, specifically within the bpf_sk_select_reuseport() function. This flaw affects the GNU/Linux subsystem of Siemens SIMATIC S7-1500 TM MFP industrial control devices. The vulnerability allows a local attacker with low privileges to trigger a denial of service condition through memory exhaustion. The CVSS 3.1 vector (AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H) indicates local attack vector, low attack complexity, low privileges required, no user interaction, and high availability impact. No confidentiality or integrity impacts are associated with this vulnerability.

Vendor: Siemens
Product: SIMATIC S7-1500 TM MFP - GNU/Linux subsystem
CVSS: MEDIUM 5.5
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 operating Siemens SIMATIC S7-1500 TM MFP devices in industrial automation environments, particularly those utilizing the GNU/Linux subsystem for custom applications or BPF-based networking configurations. Security teams responsible for OT/ICS infrastructure and system administrators managing embedded Linux subsystems on industrial controllers.

Technical summary

The bpf_sk_select_reuseport() function in the Linux kernel BPF subsystem contains a memory leak that can be triggered by local users. This vulnerability affects the GNU/Linux subsystem component of Siemens SIMATIC S7-1500 TM MFP devices. Successful exploitation leads to memory exhaustion and denial of service. The vulnerability requires local access and low privileges, with no user interaction needed. No patch is currently available from the vendor.

Defensive priority

medium

Recommended defensive actions

Restrict interactive shell access to the GNU/Linux subsystem to trusted personnel only
Build and run applications exclusively from trusted sources
Monitor system memory utilization for anomalous consumption patterns
Apply vendor patches when Siemens releases a security update for this vulnerability
Implement network segmentation to limit access to affected industrial control devices

Evidence notes

The vulnerability description indicates a memory leak in bpf_sk_select_reuseport(), a BPF helper function used for socket selection in reuseport configurations. The affected product is the GNU/Linux subsystem of Siemens SIMATIC S7-1500 TM MFP, an industrial automation device. The CVSS score of 5.5 (MEDIUM) reflects localized impact with high availability consequences. The advisory notes that currently no fix is available, requiring operational mitigations.

Official resources

2024-04-09