PatchSiren

PatchSiren cyber security CVE debrief

CVE-2025-38693 Cert Portal CVE debrief

CVE-2025-38693 is a kernel crash issue in the Linux media stack: the w7090p tuner write/read serpar paths could dereference a null buffer when message length is zero. The advisory describes a fix that adds a length check before accessing message data. CISA published the advisory on 2026-05-12 and republishes it on 2026-05-14 with Siemens ProductCERT material. The source record’s product labeling is low-confidence and appears inconsistent with the Linux-kernel description, so treat the product mapping carefully and verify affected exposure before prioritizing remediation.

Vendor
Cert Portal
Product
Siemens SIMATIC CN 4100 vers:intdot/<5.0
CVSS
HIGH 7
CISA KEV
Not listed in stored evidence
Original CVE published
2026-05-12
Original CVE updated
2026-05-14
Advisory published
2026-05-12
Advisory updated
2026-05-14

Who should care

Linux kernel maintainers, embedded and OT platform teams, Siemens SIMATIC CN 4100 operators using the referenced advisory, and defenders responsible for systems that expose or include the affected media/DVB frontend code path.

Technical summary

The vulnerability is a null-pointer dereference in w7090p_tuner_write_serpar and w7090p_tuner_read_serpar. According to the advisory text, user-controlled msg input could pass earlier buffer checks when msg[0].buf is null and msg[0].len is zero; later access to msg[0].buf[2] could trigger a kernel crash. The fix is to sanity-check msg[0].len before dereferencing the buffer. The CVSS vector provided by the source is CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H with a base score of 7.0.

Defensive priority

High for any environment that may include the affected kernel code path, because the issue can crash kernel-space functionality and the source advisory provides a vendor fix. Priority should be reduced only if you confirm the referenced component is not present in your deployed image or product build.

Recommended defensive actions

  • Update to V5.0 or later as instructed in the Siemens remediation guidance.
  • Verify whether any deployed Siemens SIMATIC CN 4100 systems or images actually include the affected code path before scheduling maintenance.
  • Review kernel/media-stack exposure on embedded or appliance systems that may incorporate DVB frontend support.
  • Monitor for unexpected kernel faults or service interruptions associated with the media subsystem until remediation is complete.
  • Use the CISA and Siemens advisories as the primary reference points for scope and fixed-version confirmation.

Evidence notes

Source text states the flaw is a null-pointer dereference in Linux kernel media: dvb-frontends: w7090p. The advisory explanation specifically calls out msg[0].buf being null while msg[0].len is zero, and recommends checking length before dereference. The supplied source metadata also shows a CISA republication on 2026-05-14 of Siemens ProductCERT SSA-032379 material. However, the source record’s product label ('Siemens SIMATIC CN 4100 vers:intdot/<5.0') does not clearly align with the Linux kernel description, so the product association should be treated as low-confidence and verified against the vendor advisory before making product-specific claims.

Official resources

CISA published the source advisory on 2026-05-12 and republished it on 2026-05-14 with Siemens ProductCERT material. Use 2026-05-12 as the CVE publication context date; the later date reflects republication, not the original vulnerability’s