5.5

CVE-2021-47418: net_sched: fix NULL deref in fifo_set_limit()

Analyzed
AliasesUBUNTU-CVE-2021-47418DEBIAN-CVE-2021-47418
Published 21-05-2024Last modified 11-05-2026

Vulnerability summary

CVE-2021-47418 is a medium (CVSS 5.5) NULL Pointer Dereference vulnerability in linux. EPSS estimates a 0.23% chance of exploitation in the next 30 days, higher than 14.3% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 5.5, local access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
5.5/10
010
Medium · v3.1 (NVD)
EPSS score
0.23%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 8 · Related 8
SUSE-SU-2024:2008-1SUSE-SU-2024:2011-1SUSE-SU-2024:2019-1SUSE-SU-2024:2189-1SUSE-SU-2024:2190-1SUSE-SU-2024:2360-1

Timeline

  1. 21-05-2024
    PublishedVulnerability first disclosed.
  2. 11-05-2026
    Last modifiedVulnerability information updated.

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

CVSS metrics

4 scores · 3 sources · 2 versions

EPSS trend

Probability

0.23%

Chance of exploitation in the next 30 days

Percentile

14%

Versus all other CVEs

30-day change

No change 0.00 pp

From 0.23% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: local access, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.

Ubuntu87 products
  • linuxAll versions (No fix recorded) | < 4.15.0-166.174 | < 5.4.0-92.103
  • linux-allwinner-5.19All versions (No fix recorded)
  • linux-awsAll versions (No fix recorded) | < 4.15.0-1118.125 | < 5.4.0-1061.64
  • linux-aws-5.0All versions (No fix recorded)
  • linux-aws-5.11All versions (No fix recorded)
Linux2 products
  • linux≥ fb0305ce1b03f6ff17f84f2c63daccecb45f2805, < 0dd7ddc462b9c2d31eb5a9926a2cc63eaa3e9f52 | ≥ fb0305ce1b03f6ff17f84f2c63daccecb45f2805, < 08d7056e8e250fd2e67dbea5be5fdecdd75bf6b4 | ≥ fb0305ce1b03f6ff17f84f2c63daccecb45f2805, < 26af64d71b6277841285fa40e3f7164a378dfda9 | ≥ fb0305ce1b03f6ff17f84f2c63daccecb45f2805, < d07098f45be868a9cdce6c616563c36c64dbbd87 | ≥ fb0305ce1b03f6ff17f84f2c63daccecb45f2805, < c951a3be5e8803e93bb49a0aca0d30457d3c1b67 | ≥ fb0305ce1b03f6ff17f84f2c63daccecb45f2805, < acff2d182c0768a713cee77442caeb07668bd68f | ≥ fb0305ce1b03f6ff17f84f2c63daccecb45f2805, < fb58cd7991747b5e0b110c98c922d7b0e47a1f14 | ≥ fb0305ce1b03f6ff17f84f2c63daccecb45f2805, < 560ee196fe9e5037e5015e2cdb14b3aecb1cd7dc | 2.6.27
  • linux_kernel≥ 2.6.27, < 4.4.289 | ≥ 4.5, < 4.9.287 | ≥ 4.10, < 4.14.251 | ≥ 4.15, < 4.19.211 | ≥ 4.20, < 5.4.153 | ≥ 5.5, < 5.10.73 | ≥ 5.11, < 5.14.12 | 5.15:rc1 | 5.15:rc2 | 5.15:rc3 | 5.15:rc4
Debian1 product
  • linux< 5.14.12-1

3 vendors · 90 products

References

12 links
Show all 12 references