CVE-2025-38125

What it actually does

Division by zero in the stmmac driver when ptp_rate is recorded as zero and later used during EST configuration, resulting in a kernel crash or denial of service.

Why it matters to the business

Affected Linux systems using stmmac Ethernet controllers may experience unexpected reboots or service interruptions during network time synchronization, with low urgency due to absence from known exploited lists and slow EPSS growth.

How an attack unfolds

An attacker with local access supplies or triggers conditions that leave ptp_rate at zero, then invokes EST configuration paths; no named threat actors are associated with this specific flaw.

How to fix it

Update the Linux kernel to commit b15c9a21950e1af6d440ce5a8edfa8a94b9acb9b or later; for AlmaLinux 10 systems also upgrade buildah and buildah-tests to 2:1.39.4-2.el10_0.

How to confirm the fix worked

Confirm the patch is present by checking for the added zero-value guard and error return in the stmmac EST configuration code; test with synthetic ptp_rate=0 inputs to verify no division occurs.

Typical attack path

1. Obtain local user access on a vulnerable Linux system
2. Trigger stmmac driver initialization that records ptp_rate as zero
3. Invoke EST configuration routines that perform division using the zero value
4. Cause kernel panic or process termination

How to detect it

Review kernel logs for division-by-zero faults or oops messages referencing stmmac and EST configuration; no specific threat-actor artifacts are known.

What your security team should do

• Prioritize kernel updates on systems exposing stmmac interfaces
• Monitor vendor advisories for backported fixes in distribution kernels
• Apply the listed AlmaLinux package updates where buildah is deployed