CVE-2023-53786

What it actually does

NULL pointer dereference crash in device-mapper flakey target when parsing table line lacking arg_name, triggered by dmsetup create with corrupt_bio_byte parameter.

Why it matters to the business

Local denial of service that can crash systems during storage device configuration or testing, increasing downtime risk in environments using device mapper; low exploitation likelihood but requires prompt patching given kernel prevalence.

How an attack unfolds

An attacker with local access crafts a dmsetup create command using an invalid flakey table line containing corrupt_bio_byte without preceding arguments, causing the kernel to dereference a NULL arg_name pointer during parsing and crash the system.

How to fix it

Upgrade affected Linux kernel to commit f95cb1526669ccdf7eb12eefd57a893953e3595f or later; for webkit2gtk on Ubuntu 18.04 update to version 2.22.2-0ubuntu0.18.04.1; rebuild and reboot systems after applying fixed packages.

How to confirm the fix worked

Confirm kernel version includes the NULL check before arg_name comparison; attempt the original crashing dmsetup command in a test environment and verify it no longer produces a NULL dereference oops.

Typical attack path

1. Obtain local shell or execution context on target system
2. Identify or create a block device such as /dev/ram0
3. Execute dmsetup create with malformed flakey table string including corrupt_bio_byte
4. Trigger NULL pointer dereference leading to kernel panic or oops

How to detect it

Review kernel logs for NULL pointer dereference oops mentioning dm_flakey or corrupt_bio_byte; inspect audit logs for dmsetup invocations with flakey tables containing corrupt_bio_byte.

What your security team should do

• Prioritize kernel updates on all systems using device-mapper flakey target
• Audit scripts and automation that invoke dmsetup for malformed table parameters
• Monitor for kernel oops logs related to dm_flakey
• Test device-mapper configurations in isolated environments before production rollout