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CVE-2025-21653 – Linux Kernel net_sched cls_flow TCA_FLOW_RSHIFT Out-of-Bounds Shift Discipline Vulnerability

The following table lists the changes that have been made to the
CVE-2025-21653 vulnerability over time.

Vulnerability history details can be useful for understanding the evolution
of a vulnerability, and for identifying the most recent changes that may
impact the vulnerability’s severity, exploitability, or other characteristics.

  • New CVE Received
    by 416baaa9-dc9f-4396-8d5f-8c081fb06d67

    Jan. 19, 2025

    Action Type Old Value New Value
    Added Description In the Linux kernel, the following vulnerability has been resolved:

    net_sched: cls_flow: validate TCA_FLOW_RSHIFT attribute

    syzbot found that TCA_FLOW_RSHIFT attribute was not validated.
    Right shitfing a 32bit integer is undefined for large shift values.

    UBSAN: shift-out-of-bounds in net/sched/cls_flow.c:329:23
    shift exponent 9445 is too large for 32-bit type ‘u32’ (aka ‘unsigned int’)
    CPU: 1 UID: 0 PID: 54 Comm: kworker/u8:3 Not tainted 6.13.0-rc3-syzkaller-00180-g4f619d518db9 #0
    Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
    Workqueue: ipv6_addrconf addrconf_dad_work
    Call Trace:

    __dump_stack lib/dump_stack.c:94 [inline]
    dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
    ubsan_epilogue lib/ubsan.c:231 [inline]
    __ubsan_handle_shift_out_of_bounds+0x3c8/0x420 lib/ubsan.c:468
    flow_classify+0x24d5/0x25b0 net/sched/cls_flow.c:329
    tc_classify include/net/tc_wrapper.h:197 [inline]
    __tcf_classify net/sched/cls_api.c:1771 [inline]
    tcf_classify+0x420/0x1160 net/sched/cls_api.c:1867
    sfb_classify net/sched/sch_sfb.c:260 [inline]
    sfb_enqueue+0x3ad/0x18b0 net/sched/sch_sfb.c:318
    dev_qdisc_enqueue+0x4b/0x290 net/core/dev.c:3793
    __dev_xmit_skb net/core/dev.c:3889 [inline]
    __dev_queue_xmit+0xf0e/0x3f50 net/core/dev.c:4400
    dev_queue_xmit include/linux/netdevice.h:3168 [inline]
    neigh_hh_output include/net/neighbour.h:523 [inline]
    neigh_output include/net/neighbour.h:537 [inline]
    ip_finish_output2+0xd41/0x1390 net/ipv4/ip_output.c:236
    iptunnel_xmit+0x55d/0x9b0 net/ipv4/ip_tunnel_core.c:82
    udp_tunnel_xmit_skb+0x262/0x3b0 net/ipv4/udp_tunnel_core.c:173
    geneve_xmit_skb drivers/net/geneve.c:916 [inline]
    geneve_xmit+0x21dc/0x2d00 drivers/net/geneve.c:1039
    __netdev_start_xmit include/linux/netdevice.h:5002 [inline]
    netdev_start_xmit include/linux/netdevice.h:5011 [inline]
    xmit_one net/core/dev.c:3590 [inline]
    dev_hard_start_xmit+0x27a/0x7d0 net/core/dev.c:3606
    __dev_queue_xmit+0x1b73/0x3f50 net/core/dev.c:4434
    Added Reference https://git.kernel.org/stable/c/2011749ca96460386844dfc7e0fde53ebee96f3c
    Added Reference https://git.kernel.org/stable/c/6fde663f7321418996645ee602a473457640542f
    Added Reference https://git.kernel.org/stable/c/a039e54397c6a75b713b9ce7894a62e06956aa92
    Added Reference https://git.kernel.org/stable/c/e54beb9aed2a90dddf4c5d68fcfc9a01f3e40a61
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