CVE-2025-71143: clk: samsung: exynos-clkout: Assign .num before accessing .hws
In the Linux kernel, the following vulnerability has been resolved:
clk: samsung: exynos-clkout: Assign .num before accessing .hws
Commit f316cdff8d67 ("clk: Annotate struct clk_hw_onecell_data with
__counted_by") annotated the hws member of 'struct clk_hw_onecell_data'
with __counted_by, which informs the bounds sanitizer (UBSAN_BOUNDS)
about the number of elements in .hws[], so that it can warn when .hws[]
is accessed out of bounds. As noted in that change, 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. This
occurs in exynos_clkout_probe() due to .num being assigned after .hws[]
has been accessed:
UBSAN: array-index-out-of-bounds in drivers/clk/samsung/clk-exynos-clkout.c:178:18
index 0 is out of range for type 'clk_hw *[*]'
Move the .num initialization to before the first access of .hws[],
clearing up the warning.
Security readout for executives and security teams
Plain-English summary
This is a Linux kernel correctness bug in the Samsung Exynos clock-output driver. A metadata field is initialized too late, causing bounds-sanitizer warnings when the driver touches its clock array. Sources describe warning cleanup, not known compromise, data exposure, or remote attack. Business impact is mainly kernel maintenance and device stability assurance.
Executive priority
Treat as routine kernel hygiene unless your fleet includes Samsung Exynos-based devices. No source indicates active exploitation or broad enterprise exposure, but affected embedded or mobile-adjacent systems should receive normal kernel update handling.
Technical view
The exynos_clkout_probe() path accesses clk_hw_onecell_data.hws before initializing .num. After __counted_by annotation, UBSAN_BOUNDS treats .num as the element count, so early access triggers an array-index-out-of-bounds warning. The fix moves .num initialization before the first .hws access.
Likely exposure
Exposure is likely limited to Linux systems using the Samsung Exynos clkout driver on affected kernel versions listed by the CVE source. General servers and non-Exynos devices are unlikely to exercise this path.
Exploitation context
The provided sources do not report active exploitation, KEV listing, public exploit activity, privilege impact, or remote attackability. Evidence supports a sanitizer-detected initialization-order bug rather than a demonstrated attack path.
Researcher notes
Key evidence is the kernel commit text: .num must be initialized before .hws access because __counted_by informs UBSAN_BOUNDS. The CVE record lacks CVSS, CWE, exploit details, and operational impact analysis, so severity confidence is constrained.
Mitigation direction
Apply the relevant Linux stable kernel fix or downstream vendor kernel update.
Prioritize Samsung Exynos platforms or kernels enabling the exynos-clkout driver.
Check distribution and device-vendor advisories for packaged fix availability.
Avoid inventing local patches; use the referenced upstream stable commits.
Validation and detection
Inventory Linux kernel versions against the CVE affected-version data.
Confirm whether the Samsung exynos-clkout driver is built or loaded.
Review boot and test logs for UBSAN_BOUNDS warnings in clk-exynos-clkout.c.
Verify the deployed kernel includes one of the referenced stable fixes.
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Potential ATT&CK relevance
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CVE reservedCVE Program
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CVE publishedCVE Program
The CVE record was published.
Jan 14, 2026, 15:07 UTC (UTC+00:00)
CVE updatedCVE Program
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