CVE-2025-38126

What it actually does

Missing validation of clk_ptp_rate allows a zero value from clk_get_rate to propagate into stmmac_init_tstamp_counter, triggering an integer divide-by-zero during PTP timestamp initialization on interface open.

Why it matters to the business

Affected Linux systems using stmmac Ethernet controllers may experience kernel crashes or boot failures when network interfaces are brought up, leading to service disruption on embedded or server platforms with high ecosystem prevalence.

How an attack unfolds

No remote attacker action is required; the flaw triggers automatically during normal interface initialization (ip_auto_config or equivalent) on hardware where device-tree-derived PTP clock rate is zero, as seen in certain STM32 and similar platforms.

How to fix it

Upgrade the Linux kernel to a version containing commit 32af9c289234990752281c805500dfe03c5b2b8f (or equivalent stable backports). Verify device-tree PTP clock entries are non-zero before enabling timestamping.

How to confirm the fix worked

Confirm kernel version includes the fix commit, then attempt interface bring-up on affected hardware while monitoring for absence of divide-by-zero in stmmac_init_tstamp_counter; inspect dmesg for the added error log on zero rate.

Typical attack path

1. Boot or hot-plug triggers stmmac platform driver load
2. clk_ptp_rate resolves to zero from device tree
3. stmmac_open calls __stmmac_open then stmmac_hw_setup
4. stmmac_init_tstamp_counter performs divide by zero
5. Kernel panics with Ldiv0_64

How to detect it

Search kernel logs and crash dumps for Ldiv0_64 and stmmac_init_tstamp_counter stack traces; correlate with interface initialization events on stmmac hardware.

What your security team should do

• Prioritize kernel updates on all stmmac-based systems within standard patch windows given low EPSS and non-KEV status
• Audit device-tree files for clk_ptp_rate definitions across embedded deployments
• Add kernel panic and stmmac-related log monitoring to existing SIEM rules