{"id":"CVE-2025-21653","title":"net_sched: cls_flow: validate TCA_FLOW_RSHIFT attribute","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet_sched: cls_flow: validate TCA_FLOW_RSHIFT attribute\n\nsyzbot found that TCA_FLOW_RSHIFT attribute was not validated.\nRight shitfing a 32bit integer is undefined for …","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= e5dfb815181fcb186d6080ac3a091eadff2d98fe < 9858f4afeb2e59506e714176bd3e135539a3eeec","Linux >= e5dfb815181fcb186d6080ac3a091eadff2d98fe < 43658e4a5f2770ad94e93362885ff51c10cf3179","Linux >= e5dfb815181fcb186d6080ac3a091eadff2d98fe < a313d6e6d5f3a631cae5a241c392c28868aa5c5e","Linux >= e5dfb815181fcb186d6080ac3a091eadff2d98fe < 2011749ca96460386844dfc7e0fde53ebee96f3c","Linux >= e5dfb815181fcb186d6080ac3a091eadff2d98fe < e54beb9aed2a90dddf4c5d68fcfc9a01f3e40a61","Linux >= e5dfb815181fcb186d6080ac3a091eadff2d98fe < 6fde663f7321418996645ee602a473457640542f","Linux >= e5dfb815181fcb186d6080ac3a091eadff2d98fe < a039e54397c6a75b713b9ce7894a62e06956aa92","Linux 2.6.25"],"published":"2025-01-19","updated":"2026-10-15","sourceUpdated":"2026-10-15T01:02:49.719Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2025-21653","references":[{"url":"https://git.kernel.org/stable/c/9858f4afeb2e59506e714176bd3e135539a3eeec"},{"url":"https://git.kernel.org/stable/c/43658e4a5f2770ad94e93362885ff51c10cf3179"},{"url":"https://git.kernel.org/stable/c/a313d6e6d5f3a631cae5a241c392c28868aa5c5e"},{"url":"https://git.kernel.org/stable/c/2011749ca96460386844dfc7e0fde53ebee96f3c"},{"url":"https://git.kernel.org/stable/c/e54beb9aed2a90dddf4c5d68fcfc9a01f3e40a61"},{"url":"https://git.kernel.org/stable/c/6fde663f7321418996645ee602a473457640542f"},{"url":"https://git.kernel.org/stable/c/a039e54397c6a75b713b9ce7894a62e06956aa92"}],"tags":["cve.org"],"epss":0.00216,"epssPercentile":0.11939,"ingestedAt":"2026-10-15T04:46:37.353Z","slug":"CVE-2025-21653","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nnet_sched: cls_flow: validate TCA_FLOW_RSHIFT attribute\n\nsyzbot found that TCA_FLOW_RSHIFT attribute was not validated.\nRight shitfing a 32bit integer is undefined for large shift values.\n\nUBSAN: shift-out-of-bounds in net/sched/cls_flow.c:329:23\nshift exponent 9445 is too large for 32-bit type 'u32' (aka 'unsigned int')\nCPU: 1 UID: 0 PID: 54 Comm: kworker/u8:3 Not tainted 6.13.0-rc3-syzkaller-00180-g4f619d518db9 #0\nHardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024\nWorkqueue: ipv6_addrconf addrconf_dad_work\nCall Trace:\n <TASK>\n  __dump_stack lib/dump_stack.c:94 [inline]\n  dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120\n  ubsan_epilogue lib/ubsan.c:231 [inline]\n  __ubsan_handle_shift_out_of_bounds+0x3c8/0x420 lib/ubsan.c:468\n  flow_classify+0x24d5/0x25b0 net/sched/cls_flow.c:329\n  tc_classify include/net/tc_wrapper.h:197 [inline]\n  __tcf_classify net/sched/cls_api.c:1771 [inline]\n  tcf_classify+0x420/0x1160 net/sched/cls_api.c:1867\n  sfb_classify net/sched/sch_sfb.c:260 [inline]\n  sfb_enqueue+0x3ad/0x18b0 net/sched/sch_sfb.c:318\n  dev_qdisc_enqueue+0x4b/0x290 net/core/dev.c:3793\n  __dev_xmit_skb net/core/dev.c:3889 [inline]\n  __dev_queue_xmit+0xf0e/0x3f50 net/core/dev.c:4400\n  dev_queue_xmit include/linux/netdevice.h:3168 [inline]\n  neigh_hh_output include/net/neighbour.h:523 [inline]\n  neigh_output include/net/neighbour.h:537 [inline]\n  ip_finish_output2+0xd41/0x1390 net/ipv4/ip_output.c:236\n  iptunnel_xmit+0x55d/0x9b0 net/ipv4/ip_tunnel_core.c:82\n  udp_tunnel_xmit_skb+0x262/0x3b0 net/ipv4/udp_tunnel_core.c:173\n  geneve_xmit_skb drivers/net/geneve.c:916 [inline]\n  geneve_xmit+0x21dc/0x2d00 drivers/net/geneve.c:1039\n  __netdev_start_xmit include/linux/netdevice.h:5002 [inline]\n  netdev_start_xmit include/linux/netdevice.h:5011 [inline]\n  xmit_one net/core/dev.c:3590 [inline]\n  dev_hard_start_xmit+0x27a/0x7d0 net/core/dev.c:3606\n  __dev_queue_xmit+0x1b73/0x3f50 net/core/dev.c:4434\n\n## Affected\n\n- `Linux >= e5dfb815181fcb186d6080ac3a091eadff2d98fe < 9858f4afeb2e59506e714176bd3e135539a3eeec`\n- `Linux >= e5dfb815181fcb186d6080ac3a091eadff2d98fe < 43658e4a5f2770ad94e93362885ff51c10cf3179`\n- `Linux >= e5dfb815181fcb186d6080ac3a091eadff2d98fe < a313d6e6d5f3a631cae5a241c392c28868aa5c5e`\n- `Linux >= e5dfb815181fcb186d6080ac3a091eadff2d98fe < 2011749ca96460386844dfc7e0fde53ebee96f3c`\n- `Linux >= e5dfb815181fcb186d6080ac3a091eadff2d98fe < e54beb9aed2a90dddf4c5d68fcfc9a01f3e40a61`\n- `Linux >= e5dfb815181fcb186d6080ac3a091eadff2d98fe < 6fde663f7321418996645ee602a473457640542f`\n- `Linux >= e5dfb815181fcb186d6080ac3a091eadff2d98fe < a039e54397c6a75b713b9ce7894a62e06956aa92`\n- `Linux 2.6.25`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}