CVE-2026-89458 s390/dasd: Do not complete a failed ESE read as successful
A local attacker can read uninitialized memory from failed ESE track reads in the Linux kernel s390/dasd driver, potentially exposing sensitive data.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-89458?
CVE-2026-89458 is a vulnerability in Linux, published on 11 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
s390/dasd: Do not complete a failed ESE read as successful
dasd_int_handler() completes an NRF read of an unallocated ESE track by calling ese_read() and unconditionally marking the request DASD_CQR_SUCCESS. dasd_eckd_ese_read() can return an error before it has zeroed the destination buffer: a failed sense-data parse or a current track outside the requested range both return early, leaving the destination pages untouched. The request is still completed successfully, so the block layer is handed stale / uninitialized memory instead of zeros.
Check the ese_read() return value and fail the request through the normal error path instead of forcing DASD_CQR_SUCCESS.
Which versions are affected by CVE-2026-89458?
How do I fix CVE-2026-89458?
Apply the vendor's patch.
Is CVE-2026-89458 being exploited?
There is no known exploitation of CVE-2026-89458 in the wild and no public exploit code.
Sources
Also known as AZL-100755, BELL-CVE-2026-89458, DEBIAN-CVE-2026-89458, GHSA-h4qc-9g56-8mx9, UBUNTU-CVE-2026-89458.