CVE-2026-31405 Linux CVE debrief

Who should care

Linux kernel maintainers, distro security teams, embedded device vendors, and operators running kernels that include the dvb-net media code path should care, especially where DVB networking features are enabled or reachable through untrusted input. Security responders should treat it as a critical kernel memory-safety bug with a public patch available.

Technical summary

In handle_one_ule_extension(), the ule_mandatory_ext_handlers[] and ule_optional_ext_handlers[] tables are declared with 255 elements, so valid indices are 0-254. The handler index htype is derived from network-controlled data as (ule_sndu_type & 0x00FF), which permits 255. That mismatch allows an out-of-bounds read from a function-pointer table. The fix adds a size check before either table is accessed; values outside the table bounds now cause the SNDU to be discarded. The weakness is categorized by NVD as CWE-125.

Defensive priority

High. This is a critical kernel issue with network-controlled input and vendor patches already available. Prioritize patching affected Linux kernel builds, especially systems that include the dvb-net path and are exposed to untrusted DVB traffic or inputs. Use the NVD version ranges to confirm whether a specific kernel build is affected.

Recommended defensive actions

• Apply the vendor or stable kernel patches referenced by NVD.
• Verify whether your kernel build falls within the affected ranges listed by NVD before and after backporting.
• If DVB networking is not required, disable or remove the relevant kernel feature set where operationally feasible.
• Rebuild and redeploy any custom or embedded kernels that may not receive automatic stable updates.
• Track the official Linux kernel release notes and distro advisories for backported fixes.
• Use the CVE published date (2026-04-06) and NVD modification date (2026-05-20) to align remediation and verification timelines.

Evidence notes

All statements are based on the supplied CVE description and NVD metadata. The issue was published on 2026-04-06 and last modified in NVD on 2026-05-20. NVD marks the CVE as analyzed, lists CVSS 3.1 9.8/CRITICAL, and includes patch references from git.kernel.org. No KEV entry was provided in the source corpus.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.