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NVD / CVE Program· CNA Linux

CVE-2021-47606: net: netlink: af_netlink: Prevent empty skb by adding a check on len.

Noroxi assessment

Priority: Monitor (action score 22/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.23% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 40cf2e058832d9cfaae98dfd77334926275598b6, 4c986072a8c9249b9398c7a18f216dc26a9f0e35, 54e785f7d5c197bc06dbb8053700df7e2a093ced.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 40cf2e058832d9cfaae98dfd77334926275598b6, 4c986072a8c9249b9398c7a18f216dc26a9f0e35, 54e785f7d5c197bc06dbb8053700df7e2a093ced or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In the Linux kernel, the following vulnerability has been resolved: net: netlink: af_netlink: Prevent empty skb by adding a check on len. Adding a check on len parameter to avoid empty skb. This prevents a division error in netem_enqueue function which is caused when skb->len=0 and skb->data_len=0 in the randomized corruption step as shown below. skb->data[prandom_u32() % skb_headlen(skb)] ^= 1<<(prandom_u32() % 8); Crash Report: [ 343.170349] netdevsim netdevsim0 netdevsim3: set [1, 0] type 2 family 0 port 6081 - 0 [ 343.216110] netem: version 1.3 [ 343.235841] divide error: 0000 [#1] PREEMPT SMP KASAN NOPTI [ 343.236680] CPU: 3 PID: 4288 Comm: reproducer Not tainted 5.16.0-rc1+ [ 343.237569] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.el7 04/01/2014 [ 343.238707] RIP: 0010:netem_enqueue+0x1590/0x33c0 [sch_netem] [ 343.239499] Code: 89 85 58 ff ff ff e8 5f 5d e9 d3 48 8b b5 48 ff ff ff 8b 8d 50 ff ff ff 8b 85 58 ff ff ff 48 8b bd 70 ff ff ff 31 d2 2b 4f 74 <f7> f1 48 b8 00 00 00 00 00 fc ff df 49 01 d5 4c 89 e9 48 c1 e9 03 [ 343.241883] RSP: 0018:ffff88800bcd7368 EFLAGS: 00010246 [ 343.242589] RAX: 00000000ba7c0a9c RBX: 0000000000000001 RCX: 0000000000000000 [ 343.243542] RDX: 0000000000000000 RSI: ffff88800f8edb10 RDI: ffff88800f8eda40 [ 343.244474] RBP: ffff88800bcd7458 R08: 0000000000000000 R09: ffffffff94fb8445 [ 343.245403] R10: ffffffff94fb8336 R11: ffffffff94fb8445 R12: 0000000000000000 [ 343.246355] R13: ffff88800a5a7000 R14: ffff88800a5b5800 R15: 0000000000000020 [ 343.247291] FS: 00007fdde2bd7700(0000) GS:ffff888109780000(0000) knlGS:0000000000000000 [ 343.248350] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 343.249120] CR2: 00000000200000c0 CR3: 000000000ef4c000 CR4: 00000000000006e0 [ 343.250076] Call Trace: [ 343.250423] <TASK> [ 343.250713] ? memcpy+0x4d/0x60 [ 343.251162] ? netem_init+0xa0/0xa0 [sch_netem] [ 343.251795] ? __sanitizer_cov_trace_pc+0x21/0x60 [ 343.252443] netem_enqueue+0xe28/0x33c0 [sch_netem] [ 343.253102] ? stack_trace_save+0x87/0xb0 [ 343.253655] ? filter_irq_stacks+0xb0/0xb0 [ 343.254220] ? netem_init+0xa0/0xa0 [sch_netem] [ 343.254837] ? __kasan_check_write+0x14/0x20 [ 343.255418] ? _raw_spin_lock+0x88/0xd6 [ 343.255953] dev_qdisc_enqueue+0x50/0x180 [ 343.256508] __dev_queue_xmit+0x1a7e/0x3090 [ 343.257083] ? netdev_core_pick_tx+0x300/0x300 [ 343.257690] ? check_kcov_mode+0x10/0x40 [ 343.258219] ? _raw_spin_unlock_irqrestore+0x29/0x40 [ 343.258899] ? __kasan_init_slab_obj+0x24/0x30 [ 343.259529] ? setup_object.isra.71+0x23/0x90 [ 343.260121] ? new_slab+0x26e/0x4b0 [ 343.260609] ? kasan_poison+0x3a/0x50 [ 343.261118] ? kasan_unpoison+0x28/0x50 [ 343.261637] ? __kasan_slab_alloc+0x71/0x90 [ 343.262214] ? memcpy+0x4d/0x60 [ 343.262674] ? write_comp_data+0x2f/0x90 [ 343.263209] ? __kasan_check_write+0x14/0x20 [ 343.263802] ? __skb_clone+0x5d6/0x840 [ 343.264329] ? __sanitizer_cov_trace_pc+0x21/0x60 [ 343.264958] dev_queue_xmit+0x1c/0x20 [ 343.265470] netlink_deliver_tap+0x652/0x9c0 [ 343.266067] netlink_unicast+0x5a0/0x7f0 [ 343.266608] ? netlink_attachskb+0x860/0x860 [ 343.267183] ? __sanitizer_cov_trace_pc+0x21/0x60 [ 343.267820] ? write_comp_data+0x2f/0x90 [ 343.268367] netlink_sendmsg+0x922/0xe80 [ 343.268899] ? netlink_unicast+0x7f0/0x7f0 [ 343.269472] ? __sanitizer_cov_trace_pc+0x21/0x60 [ 343.270099] ? write_comp_data+0x2f/0x90 [ 343.270644] ? netlink_unicast+0x7f0/0x7f0 [ 343.271210] sock_sendmsg+0x155/0x190 [ 343.271721] ____sys_sendmsg+0x75f/0x8f0 [ 343.272262] ? kernel_sendmsg+0x60/0x60 [ 343.272788] ? write_comp_data+0x2f/0x90 [ 343.273332] ? write_comp_data+0x2f/0x90 [ 343.273869] ___sys_sendmsg+0x10f/0x190 [ 343.274405] ? sendmsg_copy_msghdr+0x80/0x80 [ 343.274984] ? slab_post_alloc_hook+0x70/0x230 [ 343.275597] ? futex_wait_setup+0x240/0x240 [ 343.276175] ? security_file_alloc+0x3e/0x170 [ 343.276779] ? write_comp_d ---truncated---

MediumCVSS 5.5 · v3.1—No exploit Fix available
Published
Jun 19, 2024
Updated
Jun 17, 2026
EPSS
0.2% · 14th percentile

Report tools

JSON

Action score

22

Monitor

Low priority for now.

CVSS
22 / 40 · 5.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
linuxlinux kernel

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • linux linux kernelbefore 4.4.296
  • linux linux kernel4.5 and later · before 4.9.294
  • linux linux kernel4.10 and later · before 4.14.259
  • linux linux kernel4.15 and later · before 4.19.222
  • linux linux kernel4.20 and later · before 5.4.167
  • linux linux kernel5.5 and later · before 5.10.87
  • linux linux kernel5.11 and later · before 5.15.10
  • linux linux kernel5.16

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 3.11affected
    • bcbde0d449eda7afa8f63280b165c8300dbd00e2 and later · before c54a60c8fbaa774f828e26df79f66229a8a0e010affected · git
    • bcbde0d449eda7afa8f63280b165c8300dbd00e2 and later · before 40cf2e058832d9cfaae98dfd77334926275598b6affected · git
    • bcbde0d449eda7afa8f63280b165c8300dbd00e2 and later · before 54e785f7d5c197bc06dbb8053700df7e2a093cedaffected · git
    • bcbde0d449eda7afa8f63280b165c8300dbd00e2 and later · before ff3f517bf7138e01a17369042908a3f345c0ee41affected · git
    • bcbde0d449eda7afa8f63280b165c8300dbd00e2 and later · before c0315e93552e0d840e9edc6abd71c7db82ec8f51affected · git
    • bcbde0d449eda7afa8f63280b165c8300dbd00e2 and later · before dadce61247c6230489527cc5e343b6002d1114c5affected · git
    • bcbde0d449eda7afa8f63280b165c8300dbd00e2 and later · before 4c986072a8c9249b9398c7a18f216dc26a9f0e35affected · git
    • bcbde0d449eda7afa8f63280b165c8300dbd00e2 and later · before f123cffdd8fe8ea6c7fded4b88516a42798797d0affected · git
    • before 3.11not affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:9bpftoolbefore 7.3.0-427.31.1.el9_47.3.0-427.31.1.el9_4
AlmaLinux:9kernelbefore 5.14.0-427.31.1.el9_45.14.0-427.31.1.el9_4
AlmaLinux:9kernel-64kbefore 5.14.0-427.31.1.el9_45.14.0-427.31.1.el9_4
AlmaLinux:9kernel-64k-corebefore 5.14.0-427.31.1.el9_45.14.0-427.31.1.el9_4
AlmaLinux:9kernel-64k-debugbefore 5.14.0-427.31.1.el9_45.14.0-427.31.1.el9_4
AlmaLinux:9kernel-64k-debug-corebefore 5.14.0-427.31.1.el9_45.14.0-427.31.1.el9_4
AlmaLinux:9kernel-64k-debug-develbefore 5.14.0-427.31.1.el9_45.14.0-427.31.1.el9_4
AlmaLinux:9kernel-64k-debug-devel-matchedbefore 5.14.0-427.31.1.el9_45.14.0-427.31.1.el9_4
AlmaLinux:9kernel-64k-debug-modulesbefore 5.14.0-427.31.1.el9_45.14.0-427.31.1.el9_4
AlmaLinux:9kernel-64k-debug-modules-corebefore 5.14.0-427.31.1.el9_45.14.0-427.31.1.el9_4
AlmaLinux:9kernel-64k-debug-modules-extrabefore 5.14.0-427.31.1.el9_45.14.0-427.31.1.el9_4
AlmaLinux:9kernel-64k-develbefore 5.14.0-427.31.1.el9_45.14.0-427.31.1.el9_4
AlmaLinux:9kernel-64k-devel-matchedbefore 5.14.0-427.31.1.el9_45.14.0-427.31.1.el9_4
AlmaLinux:9kernel-64k-modulesbefore 5.14.0-427.31.1.el9_45.14.0-427.31.1.el9_4
AlmaLinux:9kernel-64k-modules-corebefore 5.14.0-427.31.1.el9_45.14.0-427.31.1.el9_4
AlmaLinux:9kernel-64k-modules-extrabefore 5.14.0-427.31.1.el9_45.14.0-427.31.1.el9_4
AlmaLinux:9kernel-abi-stablelistsbefore 5.14.0-427.31.1.el9_45.14.0-427.31.1.el9_4
AlmaLinux:9kernel-corebefore 5.14.0-427.31.1.el9_45.14.0-427.31.1.el9_4
AlmaLinux:9kernel-cross-headersbefore 5.14.0-427.31.1.el9_45.14.0-427.31.1.el9_4
AlmaLinux:9kernel-debugbefore 5.14.0-427.31.1.el9_45.14.0-427.31.1.el9_4
AlmaLinux:9kernel-debug-corebefore 5.14.0-427.31.1.el9_45.14.0-427.31.1.el9_4
AlmaLinux:9kernel-debug-develbefore 5.14.0-427.31.1.el9_45.14.0-427.31.1.el9_4
AlmaLinux:9kernel-debug-devel-matchedbefore 5.14.0-427.31.1.el9_45.14.0-427.31.1.el9_4
AlmaLinux:9kernel-debug-modulesbefore 5.14.0-427.31.1.el9_45.14.0-427.31.1.el9_4

+96

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
    90Now
  • CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV
    89Now
  • CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
    85Now

Published before and after this one in the same product

  • ← EarlierCVE-2021-47604Jun 19, 2024 · vduse: check that offset is within bounds in get_config()
    28Monitor
  • ← EarlierCVE-2021-47605Jun 19, 2024 · vduse: fix memory corruption in vduse_dev_ioctl()
    31Monitor
  • Later →CVE-2021-47607Jun 19, 2024 · bpf: Fix kernel address leakage in atomic cmpxchg's r0 aux reg
    22Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux40cf2e058832d9cfaae98dfd77334926275598b6Vendor (CNA)
Linux Linux4c986072a8c9249b9398c7a18f216dc26a9f0e35Vendor (CNA)
Linux Linux54e785f7d5c197bc06dbb8053700df7e2a093cedVendor (CNA)
Linux Linuxc0315e93552e0d840e9edc6abd71c7db82ec8f51Vendor (CNA)
Linux Linuxc54a60c8fbaa774f828e26df79f66229a8a0e010Vendor (CNA)
Linux Linuxdadce61247c6230489527cc5e343b6002d1114c5Vendor (CNA)
Linux Linuxf123cffdd8fe8ea6c7fded4b88516a42798797d0Vendor (CNA)
Linux Linuxff3f517bf7138e01a17369042908a3f345c0ee41Vendor (CNA)
almalinux:bpftool7.3.0-427.31.1.el9_4 · AlmaLinux:9Package registry (OSV)
almalinux:kernel5.14.0-427.31.1.el9_4 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k5.14.0-427.31.1.el9_4 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-core5.14.0-427.31.1.el9_4 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug5.14.0-427.31.1.el9_4 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-core5.14.0-427.31.1.el9_4 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-devel5.14.0-427.31.1.el9_4 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-devel-matched5.14.0-427.31.1.el9_4 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules5.14.0-427.31.1.el9_4 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules-core5.14.0-427.31.1.el9_4 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules-extra5.14.0-427.31.1.el9_4 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-devel5.14.0-427.31.1.el9_4 · AlmaLinux:9Package registry (OSV)
debian:linux5.15.15-1 · Debian:12Package registry (OSV)
opensuse:kernel-azure5.14.21-150500.33.63.1 · openSUSE:Leap 15.5Package registry (OSV)
opensuse:kernel-rt5.14.21-150500.13.64.1 · openSUSE:Leap Micro 5.5Package registry (OSV)
opensuse:kernel-rt_debug5.14.21-150500.13.64.1 · openSUSE:Leap 15.5Package registry (OSV)
opensuse:kernel-source-azure5.14.21-150500.33.63.1 · openSUSE:Leap 15.5Package registry (OSV)
opensuse:kernel-source-rt5.14.21-150500.13.64.1 · openSUSE:Leap 15.5Package registry (OSV)
opensuse:kernel-syms-azure5.14.21-150500.33.63.1 · openSUSE:Leap 15.5Package registry (OSV)
opensuse:kernel-syms-rt5.14.21-150500.13.64.1 · openSUSE:Leap 15.5Package registry (OSV)
red hat:bpftool-debuginfo0:7.3.0-427.31.1.el9_4 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-debug-debuginfo0:5.14.0-427.31.1.el9_4 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)

+19

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2024-2694549 days apartcrypto: iaa - Fix nr_cpus < nr_iaa case
    33Monitor
  • CVE-2021-475840 days apartiocost: Fix divide-by-zero on donation from low hweight cgroup
    22Monitor
  • CVE-2024-3696911 days apartdrm/amd/display: Fix division by zero in setup_dsc_config
    22Monitor
  • CVE-2024-3947516 days apartfbdev: savage: Handle err return when savagefb_check_var failed
    22Monitor
  • CVE-2024-3690520 days aparttcp: defer shutdown(SEND_SHUTDOWN) for TCP_SYN_RECV sockets
    22Monitor
  • CVE-2021-4749528 days apartusbnet: sanity check for maxpacket
    22Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-369 · Divide By Zero

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (7 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records