CVE-2026-98848 Linux CVE debrief

Who should care

Defenders responsible for Linux kernel maintenance and updates should assess exposure and prioritize patching to prevent potential array-index-out-of-bounds reports during probe. Operators of systems using the Linux kernel should verify their kernel version and apply patches to prevent potential array-index-out-of-bounds reports during probe. Security teams should review Linux kernel configurations to ensure secure settings and monitor Linux kernel updates

Why it matters

The vulnerability allows for an out-of-bounds warning when accessing the .hws array in the ac100_rtc_register_clks() function. Defenders should prioritize verifying the Linux kernel version and applying patches to prevent potential array-index-out-of-bounds reports during probe.

• Verify Linux kernel version to determine exposure
• Apply patches to prevent array-index-out-of-bounds reports during probe
• Review Linux kernel configurations to ensure secure settings

Technical summary

The vulnerability occurs in the ac100_rtc_register_clks() function where .num is assigned only after every clkout clock has been stored in .hws[]. This causes an array-index-out-of-bounds report during probe when CONFIG_UBSAN_BOUNDS is enabled. The __counted_by member must be initialized with the number of elements before the first array access happens, otherwise there will be a warning from each access prior to the initialization because the number of elements is zero. Initialize .num with AC100_CLKOUT_NUM, the number of elements .hws[] was allocated with, right after the allocation. That is the value the loop counter ends up at on the successful probe.

Defensive priority

Defenders should prioritize verifying the Linux kernel version and applying patches to prevent potential array-index-out-of-bounds reports during probe.

Recommended defensive actions

• Verify Linux kernel version and apply patches
• Review and update Linux kernel configurations
• Monitor Linux kernel updates and patches
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up.
• Review compensating controls for exposed systems while remediation is scheduled and verified.
• Check relevant monitoring, detection, and logs for exposed assets that need extra review.
• Track exceptions, retest remediated assets, and close the item only after evidence is documented.

Evidence notes

The vulnerability is caused by the .num member being assigned only after every clkout clock has been stored in .hws[]. The __counted_by member must be initialized with the number of elements before the first array access happens.

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.