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CVE Record

CVE-2021-47395: mac80211: limit injected vht mcs/nss in ieee80211_parse_tx_radiotap

In the Linux kernel, the following vulnerability has been resolved: mac80211: limit injected vht mcs/nss in ieee80211_parse_tx_radiotap Limit max values for vht mcs and nss in ieee80211_parse_tx_radiotap routine in order to fix the following warning reported by syzbot: WARNING: CPU: 0 PID: 10717 at include/net/mac80211.h:989 ieee80211_rate_set_vht include/net/mac80211.h:989 [inline] WARNING: CPU: 0 PID: 10717 at include/net/mac80211.h:989 ieee80211_parse_tx_radiotap+0x101e/0x12d0 net/mac80211/tx.c:2244 Modules linked in: CPU: 0 PID: 10717 Comm: syz-executor.5 Not tainted 5.14.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:ieee80211_rate_set_vht include/net/mac80211.h:989 [inline] RIP: 0010:ieee80211_parse_tx_radiotap+0x101e/0x12d0 net/mac80211/tx.c:2244 RSP: 0018:ffffc9000186f3e8 EFLAGS: 00010216 RAX: 0000000000000618 RBX: ffff88804ef76500 RCX: ffffc900143a5000 RDX: 0000000000040000 RSI: ffffffff888f478e RDI: 0000000000000003 RBP: 00000000ffffffff R08: 0000000000000000 R09: 0000000000000100 R10: ffffffff888f46f9 R11: 0000000000000000 R12: 00000000fffffff8 R13: ffff88804ef7653c R14: 0000000000000001 R15: 0000000000000004 FS: 00007fbf5718f700(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000001b2de23000 CR3: 000000006a671000 CR4: 00000000001506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600 Call Trace: ieee80211_monitor_select_queue+0xa6/0x250 net/mac80211/iface.c:740 netdev_core_pick_tx+0x169/0x2e0 net/core/dev.c:4089 __dev_queue_xmit+0x6f9/0x3710 net/core/dev.c:4165 __bpf_tx_skb net/core/filter.c:2114 [inline] __bpf_redirect_no_mac net/core/filter.c:2139 [inline] __bpf_redirect+0x5ba/0xd20 net/core/filter.c:2162 ____bpf_clone_redirect net/core/filter.c:2429 [inline] bpf_clone_redirect+0x2ae/0x420 net/core/filter.c:2401 bpf_prog_eeb6f53a69e5c6a2+0x59/0x234 bpf_dispatcher_nop_func include/linux/bpf.h:717 [inline] __bpf_prog_run include/linux/filter.h:624 [inline] bpf_prog_run include/linux/filter.h:631 [inline] bpf_test_run+0x381/0xa30 net/bpf/test_run.c:119 bpf_prog_test_run_skb+0xb84/0x1ee0 net/bpf/test_run.c:663 bpf_prog_test_run kernel/bpf/syscall.c:3307 [inline] __sys_bpf+0x2137/0x5df0 kernel/bpf/syscall.c:4605 __do_sys_bpf kernel/bpf/syscall.c:4691 [inline] __se_sys_bpf kernel/bpf/syscall.c:4689 [inline] __x64_sys_bpf+0x75/0xb0 kernel/bpf/syscall.c:4689 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 RIP: 0033:0x4665f9

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysislow

Security readout for executives and security teams

Plain-English summary

This is a Linux kernel wireless stack issue in mac80211. The fix limits invalid VHT rate values in injected radiotap transmit metadata. The public record shows a syzbot-reported kernel warning, not confirmed real-world compromise. Business urgency is mainly patch hygiene for Linux systems using affected kernels and wireless functionality.

Executive priority

Treat as routine-to-moderate Linux kernel maintenance unless affected wireless-capable systems are exposed to untrusted local users or testing workloads. No source evidence supports emergency response for active exploitation.

Technical view

CVE-2021-47395 affects ieee80211_parse_tx_radiotap in Linux mac80211. Overlarge injected VHT MCS/NSS values reached ieee80211_rate_set_vht and triggered a kernel warning. Kernel stable commits add bounds checking. The bundle does not provide CVSS, CWE, privilege requirements, or a demonstrated security impact beyond the WARN trace.

Likely exposure

Exposure appears limited to Linux systems running affected kernel versions with mac80211 wireless code reachable, especially radiotap injection paths. The source bundle does not prove remote exposure or broad default exploitability.

Exploitation context

The record is not listed as KEV and the bundle cites no active exploitation. Evidence is a syzbot kernel warning trace involving BPF test execution and mac80211 transmit parsing, not a public exploit report.

Researcher notes

Key uncertainty is impact. The public text documents a WARN from invalid radiotap VHT parameters, but does not state privilege boundary, denial-of-service reliability, memory corruption, or exploitability. Validate with kernel commit presence rather than assuming version strings alone.

Mitigation direction

  • Upgrade to a Linux kernel containing the referenced stable fixes.
  • Prioritize systems that use Wi-Fi, monitor mode, or packet injection tooling.
  • Check distribution advisories for backported kernel fixes.
  • Limit access to privileged wireless injection and BPF testing interfaces where practical.

Validation and detection

  • Inventory Linux kernel versions against vendor advisories and fixed stable commits.
  • Confirm deployed kernels include the mac80211 VHT MCS/NSS bounds check.
  • Review whether hosts load or depend on mac80211 wireless functionality.
  • Check monitoring for kernel WARN reports in mac80211 transmit paths.
Prepared
Confidence
medium
Sources
9

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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CVE-2021-47395 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
2ADP providers
8Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux646e76bb5daf4ca38438c69ffb72cccb605f3466, 646e76bb5daf4ca38438c69ffb72cccb605f3466, 646e76bb5daf4ca38438c69ffb72cccb605f3466, 646e76bb5daf4ca38438c69ffb72cccb605f3466, 646e76bb5daf4ca38438c69ffb72cccb605f3466, 646e76bb5daf4ca38438c69ffb72cccb605f3466, 646e76bb5daf4ca38438c69ffb72cccb605f3466unaffected
LinuxLinux4.7, 0, 4.9.285, 4.14.249, 4.19.209, 5.4.151, 5.10.71, 5.14.10, 5.15affected
Weakness

CWE details

No CWE listed

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