CVE-2026-31422

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

net/sched: cls_flow: fix NULL pointer dereference on shared blocks

flow_change() calls tcf_block_q() and dereferences q->handle to derive

a default baseclass. Shared blocks leave block->q NULL, causing a NULL

deref when a flow filter without a fully qualified baseclass is created

on a shared block.

Check tcf_block_shared() before accessing block->q and return -EINVAL

for shared blocks. This avoids the null-deref shown below:

=======================================================================

KASAN: null-ptr-deref in range [0x0000000000000038-0x000000000000003f]

RIP: 0010:flow_change (net/sched/cls_flow.c:508)

Call Trace:

tc_new_tfilter (net/sched/cls_api.c:2432)

rtnetlink_rcv_msg (net/core/rtnetlink.c:6980)

[...]

=======================================================================

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References