CVE-2025-38001

A use-after-free (UAF) vulnerability, which also presents a potential infinite loop condition, has been resolved in the Linux kernel. This flaw affects the HFSC (Hierarchical Fair Service Curve) queuing discipline when it is used in conjunction with NETEM (Network Emulation).

A malicious user could exploit this by repeatedly inserting a class into the eltree due to insufficient validation in prior logic, effectively bypassing the protection provided by the HFSC_RSC flag. Successful exploitation could lead to memory corruption, an infinite loop, or a system crash, severely impacting network availability and system stability.

On Red Hat Enterprise Linux 8 and later releases, regular (non-root) users can exploit this issue by abusing unprivileged user namespaces. Red Hat Enterprise Linux 6 and 7 are not affected by this CVE because they did not include the upstream commit that introduced the CVE (37d9cf1).

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.

To mitigate this issue, prevent module sch_hfsc from being loaded. Please see https://access.redhat.com/solutions/41278 for how to blacklist a kernel module to prevent it from loading automatically.