CVE-2025-38458

What it actually does

NULL pointer dereference in vcc_sendmsg() when atmarpd_dev_ops lacks a send implementation, causing kernel crash via direct call to NULL function pointer.

Why it matters to the business

Systems using ATM networking in the Linux kernel can experience sudden crashes and reboots, leading to downtime and potential data loss in environments still relying on legacy ATM configurations.

How an attack unfolds

An attacker with local access triggers the vulnerable path by invoking sendmsg on an ATM VCC socket where the device ops lack a send handler, resulting in immediate kernel NULL dereference and system instability; listed threat actors have targeted similar Linux kernel flaws for privilege escalation in container environments.

How to fix it

Apply the kernel fix from commit 9ec7e943aee5c28c173933f9defd40892fb3be3d or upgrade to a patched stable release; for libssh on Debian 13 update to 0.11.2-1 if applicable in your distribution.

How to confirm the fix worked

Verify kernel source contains the referenced commit, test ATM socket send operations do not panic, and confirm no NULL dereference in vcc_sendmsg path via code review or fuzzing.

Typical attack path

1. Obtain local user or container access on affected Linux system
2. Create or manipulate ATM VCC socket
3. Invoke sendmsg or sendmmsg syscall on the socket
4. Trigger atmarpd_dev_ops without send method, dereferencing NULL
5. Kernel oops and potential denial of service or escalation

How to detect it

Search kernel logs for NULL pointer dereference oops mentioning vcc_sendmsg, atmarpd_dev_ops, or net/atm/common.c around the time of ATM-related socket activity; correlate with unusual sendmmsg calls from untrusted processes.

What your security team should do

• Prioritize kernel updates on any systems exposing ATM or legacy networking code
• Restrict unprivileged local access and container workloads until patched
• Monitor for similar NULL dereference patterns in other protocol families
• Review EPSS trend and threat actor activity around Linux kernel networking bugs for broader context