CVE-2023-53676

What it actually does

Unchecked use of sprintf() in a loop inside lio_target_nacl_info_show() allows an iSCSI session containing a large number of connections to overflow the configfs-provided buffer, resulting in adjacent kernel memory corruption.

Why it matters to the business

Linux systems exposing iSCSI targets face risk of kernel-level memory corruption that can lead to crashes, privilege escalation, or full system compromise, potentially disrupting storage services and exposing stored data.

How an attack unfolds

An attacker establishes an iSCSI session, creates enough connections to exceed the buffer size, then triggers lio_target_nacl_info_show() through configfs to overflow memory and corrupt kernel structures for further exploitation.

How to fix it

Update the Linux kernel to a version containing commit df349e84c2cb0dd05d98c8e1189c26ab4b116083 or later; rebuild and reboot with the patched kernel. Where immediate patching is not possible, restrict access to configfs and limit iSCSI session connection counts via target configuration.

How to confirm the fix worked

Confirm the running kernel contains commit df349e84c2cb0dd05d98c8e1189c26ab4b116083 by checking git log or kernel version string; attempt to create many iSCSI connections and read the nacl_info attribute to verify no overflow occurs.

Typical attack path

1. Obtain network or local access sufficient to initiate iSCSI sessions against the target
2. Open a large number of iSCSI connections within a single session
3. Invoke the configfs attribute that calls lio_target_nacl_info_show()
4. Trigger the unbounded sprintf() loop to overflow the buffer
5. Leverage the resulting memory corruption for code execution or denial of service

How to detect it

Review kernel logs for oops or panic messages referencing lio_target_nacl_info_show or iscsi connection handling; inspect audit logs for unusual numbers of iSCSI login requests from a single initiator; correlate with configfs reads on target attributes.

What your security team should do

• Prioritize kernel updates on all systems that expose iSCSI targets
• Audit iSCSI configurations to enforce reasonable connection limits per session
• Restrict configfs access to only trusted administrative processes
• Monitor for kernel oops or crashes correlated with iSCSI activity