CVE-2025-39675 Cert Portal CVE debrief

Who should care

Defenders and operators responsible for Linux-based systems that include AMD display/HDCP components, and Siemens SIMATIC CN 4100 users tracking the referenced advisory, should review this issue. Because the source corpus ties the CVE to an OT advisory with low-confidence vendor metadata, asset owners should validate whether their deployed product or firmware actually contains the affected code path.

Technical summary

The vulnerability is a null-pointer dereference in mod_hdcp_hdcp1_create_session(). The function calls get_first_active_display() and previously did not verify whether the returned pointer was null. When the display list is empty, a null return could lead to a crash or denial of service. The fix adds a null check and returns MOD_HDCP_STATUS_DISPLAY_NOT_FOUND. The advisory references a similar prior kernel commit that added a null check for get_first_active_display().

Defensive priority

Medium. The CVSS vector supplied in the source corpus is AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H, indicating a local-impact availability issue. Prioritize this for systems where local access is plausible and where a crash in the graphics/HDCP path would materially affect operations.

Recommended defensive actions

• Update to V5.0 or later, as stated in the vendor remediation guidance.
• Confirm whether affected Linux kernel components or vendor firmware are present in your environment before scheduling maintenance.
• Review systems that rely on AMD display/HDCP functionality for stability-sensitive workloads.
• Monitor vendor and CISA advisories for any clarification of the Siemens SIMATIC CN 4100 scope or affected versions.
• Use standard ICS defense-in-depth and hardening practices referenced by CISA while remediation is being planned.

Evidence notes

The source corpus states the issue was published on 2026-05-12 and modified on 2026-05-14, with the modified entry described as an initial CISA republication of Siemens ProductCERT advisory SSA-032379. The advisory text explicitly describes a missing null check in mod_hdcp_hdcp1_create_session() and cites the return of MOD_HDCP_STATUS_DISPLAY_NOT_FOUND as the fix. The corpus also includes a vendor/product mapping to Siemens SIMATIC CN 4100 vers:intdot/<5.0, but that mapping is marked low confidence and needs review. No exploit code or weaponized details are present in this debrief.

Official resources