PatchSiren cyber security CVE debrief

CVE-2024-27436 Linux CVE debrief

A vulnerability in the Linux kernel's ALSA USB audio driver could allow a local attacker to cause a denial of service. The flaw occurs when parsing channel bits from USB audio devices that set more bits than the declared number of channels, potentially causing an out-of-bounds write to the channel map array. This affects Siemens SIMATIC S7-1500 TM MFP industrial control systems that include a GNU/Linux subsystem. The vulnerability requires local access and low privileges to exploit, with no confidentiality or integrity impact but high availability impact.

Vendor: Linux
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 industrial control systems with the GNU/Linux subsystem enabled should prioritize this vulnerability. System administrators responsible for ICS/OT environments, security teams managing industrial assets, and personnel with access to the embedded Linux shell on affected devices are the primary stakeholders. The vulnerability is particularly relevant in environments where USB devices may connect to the industrial system.

Technical summary

The vulnerability exists in the ALSA (Advanced Linux Sound Architecture) USB audio driver within the Linux kernel. When parsing channel configuration bits from a USB audio device, the driver fails to validate that the number of bits set does not exceed the declared channel count. A malicious or malformed USB audio device can set more channel bits than the allocated map array size, resulting in an out-of-bounds write. This is classified as CWE-20 (Improper Input Validation). The vulnerability was fixed by stopping channel bit parsing once all expected channels are found, preventing the overflow condition.

Defensive priority

medium

Recommended defensive actions

Limit access to the interactive shell of the additional GNU/Linux subsystem to trusted personnel only
Only build and run applications from trusted sources
Monitor for kernel updates from Siemens for the SIMATIC S7-1500 TM MFP GNU/Linux subsystem
Apply defense-in-depth strategies for industrial control systems per CISA guidance

Evidence notes

The vulnerability was disclosed in the Linux kernel ALSA USB audio subsystem. CISA published advisory ICSA-24-102-01 on 2024-04-09, with subsequent updates through 2025-09-09 adding additional CVEs to the same advisory. Siemens published security advisory SSA-265688 covering this vulnerability in their SIMATIC S7-1500 TM MFP product. The CVSS 3.1 vector confirms local attack vector with low attack complexity.

Official resources

2024-04-09