{
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"cveMetadata": {
"cveId": "CVE-2026-53080",
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"state": "PUBLISHED",
"assignerShortName": "Linux",
"dateReserved": "2026-06-09T07:44:35.383Z",
"datePublished": "2026-06-24T16:30:21.172Z",
"dateUpdated": "2026-10-15T01:22:21.282Z"
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"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: cls_fw: fix NULL dereference of \"old\" filters before change()\n\nLike pointed out by Sashiko [1], since commit ed76f5edccc9 (\"net: sched:\nprotect filter_chain list with filter_chain_lock mutex\") TC filters are\nadded to a shared block and published to datapath before their ->change()\nfunction is called. This is a problem for cls_fw: an invalid filter\ncreated with the \"old\" method can still classify some packets before it\nis destroyed by the validation logic added by Xiang.\nTherefore, insisting with repeated runs of the following script:\n\n # ip link add dev crash0 type dummy\n # ip link set dev crash0 up\n # mausezahn crash0 -c 100000 -P 10 \\\n > -A 4.3.2.1 -B 1.2.3.4 -t udp \"dp=1234\" -q &\n # sleep 1\n # tc qdisc add dev crash0 egress_block 1 clsact\n # tc filter add block 1 protocol ip prio 1 matchall \\\n > action skbedit mark 65536 continue\n # tc filter add block 1 protocol ip prio 2 fw\n # ip link del dev crash0\n\ncan still make fw_classify() hit the WARN_ON() in [2]:\n\n WARNING: ./include/net/pkt_cls.h:88 at fw_classify+0x244/0x250 [cls_fw], CPU#18: mausezahn/1399\n Modules linked in: cls_fw(E) act_skbedit(E)\n CPU: 18 UID: 0 PID: 1399 Comm: mausezahn Tainted: G E 7.0.0-rc6-virtme #17 PREEMPT(full)\n Tainted: [E]=UNSIGNED_MODULE\n Hardware name: Red Hat KVM, BIOS 1.16.3-2.el9 04/01/2014\n RIP: 0010:fw_classify+0x244/0x250 [cls_fw]\n Code: 5c 49 c7 45 00 00 00 00 00 41 5d 41 5e 41 5f 5d c3 cc cc cc cc 5b b8 ff ff ff ff 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc 90 <0f> 0b 90 eb a0 0f 1f 80 00 00 00 00 90 90 90 90 90 90 90 90 90 90\n RSP: 0018:ffffd1b7026bf8a8 EFLAGS: 00010202\n RAX: ffff8c5ac9c60800 RBX: ffff8c5ac99322c0 RCX: 0000000000000004\n RDX: 0000000000000001 RSI: ffff8c5b74d7a000 RDI: ffff8c5ac8284f40\n RBP: ffffd1b7026bf8d0 R08: 0000000000000000 R09: ffffd1b7026bf9b0\n R10: 00000000ffffffff R11: 0000000000000000 R12: 0000000000010000\n R13: ffffd1b7026bf930 R14: ffff8c5ac8284f40 R15: 0000000000000000\n FS: 00007fca40c37740(0000) GS:ffff8c5b74d7a000(0000) knlGS:0000000000000000\n CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n CR2: 00007fca40e822a0 CR3: 0000000005ca0001 CR4: 0000000000172ef0\n Call Trace:\n \n tcf_classify+0x17d/0x5c0\n tc_run+0x9d/0x150\n __dev_queue_xmit+0x2ab/0x14d0\n ip_finish_output2+0x340/0x8f0\n ip_output+0xa4/0x250\n raw_sendmsg+0x147d/0x14b0\n __sys_sendto+0x1cc/0x1f0\n __x64_sys_sendto+0x24/0x30\n do_syscall_64+0x126/0xf80\n entry_SYSCALL_64_after_hwframe+0x77/0x7f\n RIP: 0033:0x7fca40e822ba\n Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb b8 0f 1f 00 f3 0f 1e fa 41 89 ca 64 8b 04 25 18 00 00 00 85 c0 75 15 b8 2c 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 7e c3 0f 1f 44 00 00 41 54 48 83 ec 30 44 89\n RSP: 002b:00007ffc248a42c8 EFLAGS: 00000246 ORIG_RAX: 000000000000002c\n RAX: ffffffffffffffda RBX: 000055ef233289d0 RCX: 00007fca40e822ba\n RDX: 000000000000001e RSI: 000055ef23328c30 RDI: 0000000000000003\n RBP: 000055ef233289d0 R08: 00007ffc248a42d0 R09: 0000000000000010\n R10: 0000000000000000 R11: 0000000000000246 R12: 000000000000001e\n R13: 00000000000186a0 R14: 0000000000000000 R15: 00007fca41043000\n \n irq event stamp: 1045778\n hardirqs last enabled at (1045784): [] __up_console_sem+0x52/0x60\n hardirqs last disabled at (1045789): [] __up_console_sem+0x37/0x60\n softirqs last enabled at (1045426): [] __alloc_skb+0x207/0x260\n softirqs last disabled at (1045434): [] __dev_queue_xmit+0x78/0x14d0\n\nThen, because of the value in the packet's mark, dereference on 'q->handle'\nwith NULL 'q' occurs:\n\n BUG: kernel NULL pointer dereference, address: 0000000000000038\n [...]\n RIP: 0010:fw_classify+0x1fe/0x250 [cls_fw]\n [...]\n\nSkip \"old-style\" classification on shared blocks, so that the NULL\ndereference is fixed and WARN_ON() is not hit anymore in the short\nlifetime of invalid cls_fw \"old-style\" filters.\n\n[1] https://sashiko.dev/#/patchset/2\n---truncated---"
}
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"status": "affected"
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"status": "unaffected",
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"status": "unaffected",
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"status": "unaffected",
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"references": [
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"url": "https://git.kernel.org/stable/c/a719275da488835e987d28effc04679b4aace3a0"
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"url": "https://git.kernel.org/stable/c/c205da704c84eeb4247d770150440294fd547049"
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"url": "https://git.kernel.org/stable/c/5dcce34c57d5e5990869384d69deeb9414bf9b92"
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"url": "https://git.kernel.org/stable/c/4fabcfea7a9dd159df32c5df6587fe858cb0d748"
},
{
"url": "https://git.kernel.org/stable/c/65782b2db7321d5f97c16718c4c7f6c7205a56be"
}
],
"title": "net/sched: cls_fw: fix NULL dereference of \"old\" filters before change()",
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