EPSS
0.045%
Advisory Published
Updated

CVE-2025-21653: net_sched: cls_flow: validate TCA_FLOW_RSHIFT attribute

First published: Sun Jan 19 2025(Updated: )

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: <TASK> __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

Credit: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

Affected SoftwareAffected VersionHow to fix
Linux Kernel
debian/linux<=5.10.223-1
5.10.234-1
6.1.129-1
6.1.128-1
6.12.21-1
debian/linux-6.1
6.1.129-1~deb11u1

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Frequently Asked Questions

  • What is the severity of CVE-2025-21653?

    CVE-2025-21653 has a high severity due to its potential for exploitation leading to undefined behavior in the Linux kernel.

  • How do I fix CVE-2025-21653?

    To fix CVE-2025-21653, update your Linux kernel to a version that includes the patch addressing the TCA_FLOW_RSHIFT attribute validation.

  • What systems are affected by CVE-2025-21653?

    CVE-2025-21653 affects the Linux kernel across various distributions and versions.

  • What are the consequences of exploiting CVE-2025-21653?

    Exploiting CVE-2025-21653 may lead to system instability or arbitrary code execution due to undefined behavior.

  • When was CVE-2025-21653 discovered?

    CVE-2025-21653 was discovered and reported by syzbot in relation to the validation of the TCA_FLOW_RSHIFT attribute.

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