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Linux KernelOperating system · Linux

CVE-2021-47175

HIGH · 7.1 CVSS v3.1 Published 2024-03-25
Fix available
A fix is available. Upgrade to 5.10.42 / 5.12.9 or later.
See remediation →
73/100
Remediation priority · Elevated
Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
In the Linux kernel, the following vulnerability has been resolved: net/sched: fq_pie: fix OOB access in the traffic path the following script: # tc qdisc add dev eth0 handle 0x1 root fq_pie flows 2 # tc qdisc add dev eth0 clsact # tc filter add dev eth0 egress matchall action skbedit priority 0x10002 # ping 192.0.2.2 -I eth0 -c2 -w1 -q produces the following splat: BUG: KASAN: slab-out-of-bounds in fq_pie_qdisc_enqueue+0x1314/0x19d0 [sch_fq_pie] Read of size 4 at addr ffff888171306924 by task ping/942 CPU: 3 PID: 942 Comm: ping Not tainted 5.12.0+ #441 Hardware name: Red Hat KVM, BIOS 1.11.1-4.module+el8.1.0+4066+0f1aadab 04/01/2014 Call Trace: dump_stack+0x92/0xc1 print_address_description.constprop.7+0x1a/0x150 kasan_report.cold.13+0x7f/0x111 fq_pie_qdisc_enqueue+0x1314/0x19d0 [sch_fq_pie] __dev_queue_xmit+0x1034/0x2b10 ip_finish_output2+0xc62/0x2120 __ip_finish_output+0x553/0xea0 ip_output+0x1ca/0x4d0 ip_send_skb+0x37/0xa0 raw_sendmsg+0x1c4b/0x2d00 sock_sendmsg+0xdb/0x110 __sys_sendto+0x1d7/0x2b0 __x64_sys_sendto+0xdd/0x1b0 do_syscall_64+0x3c/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7fe69735c3eb Code: 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 f3 0f 1e fa 48 8d 05 75 42 2c 00 41 89 ca 8b 00 85 c0 75 14 b8 2c 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 75 c3 0f 1f 40 00 41 57 4d 89 c7 41 56 41 89 RSP: 002b:00007fff06d7fb38 EFLAGS: 00000246 ORIG_RAX: 000000000000002c RAX: ffffffffffffffda RBX: 000055e961413700 RCX: 00007fe69735c3eb RDX: 0000000000000040 RSI: 000055e961413700 RDI: 0000000000000003 RBP: 0000000000000040 R08: 000055e961410500 R09: 0000000000000010 R10: 0000000000000000 R11: 0000000000000246 R12: 00007fff06d81260 R13: 00007fff06d7fb40 R14: 00007fff06d7fc30 R15: 000055e96140f0a0 Allocated by task 917: kasan_save_stack+0x19/0x40 __kasan_kmalloc+0x7f/0xa0 __kmalloc_node+0x139/0x280 fq_pie_init+0x555/0x8e8 [sch_fq_pie] qdisc_create+0x407/0x11b0 tc_modify_qdisc+0x3c2/0x17e0 rtnetlink_rcv_msg+0x346/0x8e0 netlink_rcv_skb+0x120/0x380 netlink_unicast+0x439/0x630 netlink_sendmsg+0x719/0xbf0 sock_sendmsg+0xe2/0x110 ____sys_sendmsg+0x5ba/0x890 ___sys_sendmsg+0xe9/0x160 __sys_sendmsg+0xd3/0x170 do_syscall_64+0x3c/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xae The buggy address belongs to the object at ffff888171306800 which belongs to the cache kmalloc-256 of size 256 The buggy address is located 36 bytes to the right of 256-byte region [ffff888171306800, ffff888171306900) The buggy address belongs to the page: page:00000000bcfb624e refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x171306 head:00000000bcfb624e order:1 compound_mapcount:0 flags: 0x17ffffc0010200(slab|head|node=0|zone=2|lastcpupid=0x1fffff) raw: 0017ffffc0010200 dead000000000100 dead000000000122 ffff888100042b40 raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff888171306800: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff888171306880: 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc >ffff888171306900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ^ ffff888171306980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888171306a00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fix fq_pie traffic path to avoid selecting 'q->flows + q->flows_cnt' as a valid flow: it's an address beyond the allocated memory.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis
How this class of weakness works · CWE-125

The code reads past the end (or before the start) of a buffer, returning memory that was never meant to be exposed. Attackers use it to leak secrets like keys or to defeat memory-protection defences. Remediation is validating indices and lengths before every read.

General guidance for the out-of-bounds read class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:>= 5.6, < 5.10.42>= 5.11, < 5.12.9= 5.13

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 5.10.42 / 5.12.9 or later
Fixed in 5.10.425.12.9
Vendor patch git.kernel.org →
Recommended fix High confidence

5.10.42+, 5.12.9+, or 5.13.1+ (depending on current branch)

  1. Update the Linux kernel to version 5.10.42 or later for 5.10.x kernels
  2. Update the Linux kernel to version 5.12.9 or later for 5.11.x or 5.12.x kernels
  3. Update the Linux kernel to any version after 5.13.0 that includes the stable patch (e.g., 5.13.1 or later) for 5.13.x kernels
  4. Reboot the system after applying the kernel update to load the patched kernel
Caveat Kernel upgrades may require rebuilding out-of-tree modules and could introduce compatibility changes with existing system configurations

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $3,200. Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-47175 in production — separate from our analysis above.

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