EUVD-2026-21946
GHSA-6pmm-j8mh-qwgf
CVSS VectorNVD
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Lifecycle Timeline
6DescriptionNVD
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) [...] ===============
AnalysisAI
NULL pointer dereference in the Linux kernel's net/sched cls_flow traffic classifier allows a local low-privileged attacker to crash the kernel (denial of service) by creating a flow filter on a shared traffic control block without a fully qualified baseclass. The crash occurs in flow_change() at net/sched/cls_flow.c:508, confirmed by a KASAN trace showing null-ptr-deref when block->q is dereferenced on a shared block where it is intentionally NULL. …
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