Medium [CVE-2025-9640] Samba: vfs_streams_xattr uninitialized memory write possible

A flaw was found in Samba, in the vfs_streams_xattr module, where uninitialized heap memory could be written into alternate data streams. This allows an authenticated user to read residual memory content that may include sensitive data, resulting in an information disclosure vulnerability.

This vulnerability is rated Low because its exploitation scope and potential impact are tightly constrained. Technically, the flaw only allows disclosure of uninitialized heap memory fragments, not direct control or corruption of memory.

The attacker must already be an authenticated user with write access to files using the vfs_streams_xattr module, significantly reducing the attack surface.

The exposed data is non-deterministic and contextually limited—it consists of residual memory content that may or may not contain meaningful information, with no guarantee of retrieving sensitive secrets. Additionally, Samba already clears known secret buffers before freeing memory, further lowering the risk of credential or key exposure.

Red Hat severity: Low — CVSS 4.3 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N). Weakness: CWE-908.

Affected Red Hat products: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 7; Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9; Red Hat OpenShift Container Platform 4. Red Hat does not currently list a fixing RHSA for this CVE.