CVE-2022-39842 Siemens CVE debrief

Who should care

Siemens SCALANCE WAB/WAM/WUB/WUM device operators, OT and plant network administrators, industrial asset owners using the affected wireless products, and security teams responsible for embedded Linux-based equipment in industrial environments.

Technical summary

According to the advisory, CVE-2022-39842 affects the Linux kernel before 5.19 in drivers/video/fbdev/pxa3xx-gcu.c. In pxa3xx_gcu_write, the count parameter is handled with a type conflict between size_t and int, which can create an integer overflow and bypass a size check. That value is then used as the third argument to copy_from_user(), creating a potential heap overflow condition. The supplied corpus also records the discoverer’s dispute that the overflow can actually happen, so the practical impact is not fully settled in the source material. Siemens maps this issue to multiple SCALANCE product variants and provides a firmware update path.

Defensive priority

Medium-high for affected OT environments. The CVSS score is 6.1 (medium), but the issue touches memory safety in deployed industrial devices and has a vendor fix available. Prioritize patching any exposed or operationally critical SCALANCE devices, especially where local access is possible or embedded Linux components are hard to monitor.

Recommended defensive actions

• Update affected Siemens SCALANCE products to V3.0.0 or later, as directed in the Siemens remediation.
• Verify whether any of the listed SCALANCE WAB/WAM/WUB/WUM models are present in your environment and map them to the affected product IDs in the advisory.
• Apply the update through normal maintenance windows and confirm firmware version after remediation.
• Restrict and review local access paths to the device and its management interfaces, since the CVSS vector indicates local attack requirements.
• Segment OT networks and limit unnecessary administrative access to reduce exposure to local attacks.
• Monitor for unusual device behavior, crashes, or unexpected maintenance activity around affected assets.
• Track Siemens advisory SSA-769027 and CISA advisory ICSA-25-044-09 for any updates or clarification on exploitability.

Evidence notes

The supplied source corpus ties CVE-2022-39842 to Siemens advisory SSA-769027 and CISA CSAF advisory ICSA-25-044-09, published on 2025-02-11 and revised on 2025-05-06 for typo fixes. The advisory lists 19 affected Siemens SCALANCE product variants and recommends updating to V3.0.0 or later. The vulnerability description states that the overflow may occur, but also explicitly notes that the original discoverer disputes whether the overflow can actually happen. The CVSS vector in the corpus is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H, which supports a local-access, privilege-requiring defensive posture rather than broad remote-exploit assumptions.

Official resources