CVE-2026-89458

A flaw was found in the Linux kernel's s390/dasd component. The dasd_int_handler() function incorrectly marks failed Extended Sense Data (ESE) read operations as successful when processing unallocated ESE tracks. This leads to the block layer receiving stale or uninitialized memory instead of properly zeroed memory. A local attacker could exploit this vulnerability to potentially gain access to sensitive information, resulting in information disclosure.

An s390 DASD ESE read of an unallocated track could be completed as successful even when ese_read failed before zeroing the destination buffer. In that case the block layer may receive stale or uninitialized memory instead of the expected zero filled data, which can expose sensitive data or return incorrect file or block contents. For the CVSS the PR:L is used because a local user or process with read access to the affected storage path may be enough to observe returned data, while administrative privileges are not necessarily required for every mounted filesystem case. The issue is not network reachable and depends on s390 DASD ESE thin provisioned devices plus a failed ESE read path, so AC:H is used. Impact is mainly confidentiality disclosure with limited integrity impact from incorrect read data, and possible limited availability impact in the paranoid score if stale data disrupts higher layer storage handling.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.