CVE-2021-47418
net_sched: fix NULL deref in fifo_set_limit()
- Published
- Updated
- Reserved
- Assigned by
- Linux
Description
In the Linux kernel, the following vulnerability has been resolved: net_sched: fix NULL deref in fifo_set_limit() syzbot reported another NULL deref in fifo_set_limit() [1] I could repro the issue with : unshare -n tc qd add dev lo root handle 1:0 tbf limit 200000 burst 70000 rate 100Mbit tc qd replace dev lo parent 1:0 pfifo_fast tc qd change dev lo root handle 1:0 tbf limit 300000 burst 70000 rate 100Mbit pfifo_fast does not have a change() operation. Make fifo_set_limit() more robust about this. [1] BUG: kernel NULL pointer dereference, address: 0000000000000000 PGD 1cf99067 P4D 1cf99067 PUD 7ca49067 PMD 0 Oops: 0010 [#1] PREEMPT SMP KASAN CPU: 1 PID: 14443 Comm: syz-executor959 Not tainted 5.15.0-rc3-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:0x0 Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6. RSP: 0018:ffffc9000e2f7310 EFLAGS: 00010246 RAX: dffffc0000000000 RBX: ffffffff8d6ecc00 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffff888024c27910 RDI: ffff888071e34000 RBP: ffff888071e34000 R08: 0000000000000001 R09: ffffffff8fcfb947 R10: 0000000000000001 R11: 0000000000000000 R12: ffff888024c27910 R13: ffff888071e34018 R14: 0000000000000000 R15: ffff88801ef74800 FS: 00007f321d897700(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffffffffffffd6 CR3: 00000000722c3000 CR4: 00000000003506e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: fifo_set_limit net/sched/sch_fifo.c:242 [inline] fifo_set_limit+0x198/0x210 net/sched/sch_fifo.c:227 tbf_change+0x6ec/0x16d0 net/sched/sch_tbf.c:418 qdisc_change net/sched/sch_api.c:1332 [inline] tc_modify_qdisc+0xd9a/0x1a60 net/sched/sch_api.c:1634 rtnetlink_rcv_msg+0x413/0xb80 net/core/rtnetlink.c:5572 netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2504 netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline] netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1340 netlink_sendmsg+0x86d/0xdb0 net/netlink/af_netlink.c:1929 sock_sendmsg_nosec net/socket.c:704 [inline] sock_sendmsg+0xcf/0x120 net/socket.c:724 ____sys_sendmsg+0x6e8/0x810 net/socket.c:2409 ___sys_sendmsg+0xf3/0x170 net/socket.c:2463 __sys_sendmsg+0xe5/0x1b0 net/socket.c:2492 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae
Timeline
ID reserved
By Linux
Published
- 24 months later
· 24 months later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| NVDNVD · Analyzed | 3.1 | Medium5.5 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H |
- EPSS (exploitation in 30 days)
- 0.23% · top 86% of all CVEs (7 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.5.
Weakness
Affected products
- affected fb0305ce1b03f6ff17f84f2c63daccecb45f2805 – < 0dd7ddc462b9c2d31eb5a9926a2cc63eaa3e9f52
- affected fb0305ce1b03f6ff17f84f2c63daccecb45f2805 – < 08d7056e8e250fd2e67dbea5be5fdecdd75bf6b4
- affected fb0305ce1b03f6ff17f84f2c63daccecb45f2805 – < 26af64d71b6277841285fa40e3f7164a378dfda9
- affected fb0305ce1b03f6ff17f84f2c63daccecb45f2805 – < d07098f45be868a9cdce6c616563c36c64dbbd87
- affected fb0305ce1b03f6ff17f84f2c63daccecb45f2805 – < c951a3be5e8803e93bb49a0aca0d30457d3c1b67
- affected fb0305ce1b03f6ff17f84f2c63daccecb45f2805 – < acff2d182c0768a713cee77442caeb07668bd68f
- affected fb0305ce1b03f6ff17f84f2c63daccecb45f2805 – < fb58cd7991747b5e0b110c98c922d7b0e47a1f14
- affected fb0305ce1b03f6ff17f84f2c63daccecb45f2805 – < 560ee196fe9e5037e5015e2cdb14b3aecb1cd7dc
- affected 2.6.27
- unaffected < 2.6.27
- unaffected 4.4.289 – ≤ 4.4.*
- unaffected 4.9.287 – ≤ 4.9.*
- unaffected 4.14.251 – ≤ 4.14.*
- unaffected 4.19.211 – ≤ 4.19.*
- unaffected 5.4.153 – ≤ 5.4.*
- unaffected 5.10.73 – ≤ 5.10.*
- unaffected 5.14.12 – ≤ 5.14.*
- unaffected 5.15 – ≤ *
References (8)
- https://git.kernel.org/stable/c/0dd7ddc462b9c2d31eb5a9926a2cc63eaa3e9f52 (opens in a new tab)x_transferred
- https://git.kernel.org/stable/c/08d7056e8e250fd2e67dbea5be5fdecdd75bf6b4 (opens in a new tab)x_transferred
- https://git.kernel.org/stable/c/26af64d71b6277841285fa40e3f7164a378dfda9 (opens in a new tab)x_transferred
- https://git.kernel.org/stable/c/d07098f45be868a9cdce6c616563c36c64dbbd87 (opens in a new tab)x_transferred
- https://git.kernel.org/stable/c/c951a3be5e8803e93bb49a0aca0d30457d3c1b67 (opens in a new tab)x_transferred
- https://git.kernel.org/stable/c/acff2d182c0768a713cee77442caeb07668bd68f (opens in a new tab)x_transferred
- https://git.kernel.org/stable/c/fb58cd7991747b5e0b110c98c922d7b0e47a1f14 (opens in a new tab)x_transferred
- https://git.kernel.org/stable/c/560ee196fe9e5037e5015e2cdb14b3aecb1cd7dc (opens in a new tab)x_transferred
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
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[](https://trackcve.app/cve/CVE-2021-47418)Record last updated .