CVE-2021-47540

MEDIUMNVD 5.55.5

Also known asEUVD-2021-34542 (ENISA EUVD)Source: ENISA EUVD

5.5EG

EchelonGraph verdictMonitorRemediate within your standard update timelines (the SSVC decision on this page).

Lower severity and no public exploit yet

CISA-KEV: Not listedEPSS PROB: 0.2%CVSS: 5.5Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

In the Linux kernel, the following vulnerability has been resolved:

mt76: mt7915: fix NULL pointer dereference in mt7915_get_phy_mode

Fix the following NULL pointer dereference in mt7915_get_phy_mode routine adding an ibss interface to the mt7915 driver.

[ 101.137097] wlan0: Trigger new scan to find an IBSS to join [ 102.827039] wlan0: Creating new IBSS network, BSSID 26:a4:50:1a:6e:69 [ 103.064756] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 [ 103.073670] Mem abort info: [ 103.076520] ESR = 0x96000005 [ 103.079614] EC = 0x25: DABT (current EL), IL = 32 bits [ 103.084934] SET = 0, FnV = 0 [ 103.088042] EA = 0, S1PTW = 0 [ 103.091215] Data abort info: [ 103.094104] ISV = 0, ISS = 0x00000005 [ 103.098041] CM = 0, WnR = 0 [ 103.101044] user pgtable: 4k pages, 39-bit VAs, pgdp=00000000460b1000 [ 103.107565] [0000000000000000] pgd=0000000000000000, p4d=0000000000000000, pud=0000000000000000 [ 103.116590] Internal error: Oops: 96000005 [#1] SMP [ 103.189066] CPU: 1 PID: 333 Comm: kworker/u4:3 Not tainted 5.10.75 #0 [ 103.195498] Hardware name: MediaTek MT7622 RFB1 board (DT) [ 103.201124] Workqueue: phy0 ieee80211_iface_work [mac80211] [ 103.206695] pstate: 20000005 (nzCv daif -PAN -UAO -TCO BTYPE=--) [ 103.212705] pc : mt7915_get_phy_mode+0x68/0x120 [mt7915e] [ 103.218103] lr : mt7915_mcu_add_bss_info+0x11c/0x760 [mt7915e] [ 103.223927] sp : ffffffc011cdb9e0 [ 103.227235] x29: ffffffc011cdb9e0 x28: ffffff8006563098 [ 103.232545] x27: ffffff8005f4da22 x26: ffffff800685ac40 [ 103.237855] x25: 0000000000000001 x24: 000000000000011f [ 103.243165] x23: ffffff8005f4e260 x22: ffffff8006567918 [ 103.248475] x21: ffffff8005f4df80 x20: ffffff800685ac58 [ 103.253785] x19: ffffff8006744400 x18: 0000000000000000 [ 103.259094] x17: 0000000000000000 x16: 0000000000000001 [ 103.264403] x15: 000899c3a2d9d2e4 x14: 000899bdc3c3a1c8 [ 103.269713] x13: 0000000000000000 x12: 0000000000000000 [ 103.275024] x11: ffffffc010e30c20 x10: 0000000000000000 [ 103.280333] x9 : 0000000000000050 x8 : ffffff8006567d88 [ 103.285642] x7 : ffffff8006563b5c x6 : ffffff8006563b44 [ 103.290952] x5 : 0000000000000002 x4 : 0000000000000001 [ 103.296262] x3 : 0000000000000001 x2 : 0000000000000001 [ 103.301572] x1 : 0000000000000000 x0 : 0000000000000011 [ 103.306882] Call trace: [ 103.309328] mt7915_get_phy_mode+0x68/0x120 [mt7915e] [ 103.314378] mt7915_bss_info_changed+0x198/0x200 [mt7915e] [ 103.319941] ieee80211_bss_info_change_notify+0x128/0x290 [mac80211] [ 103.326360] __ieee80211_sta_join_ibss+0x308/0x6c4 [mac80211] [ 103.332171] ieee80211_sta_create_ibss+0x8c/0x10c [mac80211] [ 103.337895] ieee80211_ibss_work+0x3dc/0x614 [mac80211] [ 103.343185] ieee80211_iface_work+0x388/0x3f0 [mac80211] [ 103.348495] process_one_work+0x288/0x690 [ 103.352499] worker_thread+0x70/0x464 [ 103.356157] kthread+0x144/0x150 [ 103.359380] ret_from_fork+0x10/0x18 [ 103.362952] Code: 394008c3 52800220 394000e4 7100007f (39400023)

CVSS v3: 5.5
EG Score: 5.5MEDIUMmedium confidence
EG Risk: 25
EPSS PROB: 0.2%
EPSS %ILE: 14th
KEV: Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (5.5): severity, escalated by confirmed exploitation. This CVE's 5.5 is its impact severity (EG Severity), not escalated.

EG Severity: 5.5 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.NVD CVSS v3 · CVSS v3.0 or v3.1
EG Likelihood: 0.2% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-25). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation: None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority: SSVC Track at medium mission impactTrack at every mission impact level.CISA BOD 26-04: 60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at every mission impact level.

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

May 24, 2024

Last Modified

November 21, 2024

References (3)

CVE Programhttps://git.kernel.org/stable/c/14b03b8cebdf18ff13c39d58501b625411314de2Patch
CVE Programhttps://git.kernel.org/stable/c/6e53d6d26920d5221d3f4d4f5ffdd629ea69aa5cPatch
CVE Programhttps://git.kernel.org/stable/c/932b338f4e5c4cb0c2ed640da3bced1e63620198Patch

Affected Packages

(4 across 4 ecosystems)

Debian:11(1)

Package	Vulnerable range	Fix by version range	Dependents
linux	5.10.46-4, 5.10.46-5, 5.10.70-1, 5.10.70-1~bpo10+1	every version up to 5.10.84-1: fixed in 5.10.84-1	—

Debian:12(1)

Package	Vulnerable range	Fix by version range	Dependents
linux	—	every version up to 5.15.15-1: fixed in 5.15.15-1	—

Debian:13(1)

Package	Vulnerable range	Fix by version range	Dependents
linux	—	every version up to 5.15.15-1: fixed in 5.15.15-1	—

Debian:14(1)

Package	Vulnerable range	Fix by version range	Dependents
linux	—	every version up to 5.15.15-1: fixed in 5.15.15-1	—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

CWE-476NULL Pointer Dereference

Data Freshness Timeline

(refreshed 7× in last 7d / 36× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

Showing the most recent 97 of 203 refreshes on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 3 repeat rows among the latest 100 are merged into the row they repeat. The 106 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

2026-11-02 16:38 UTCEPSS rescoreEPSS 0.2% · 14th percentile
2026-11-01 16:30 UTCEPSS rescoreEPSS 0.2% · 14th percentile
2026-10-31 16:29 UTCEPSS rescoreEPSS 0.2% · 14th percentile
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2026-10-25 18:18 UTCEG score recompute
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2026-10-24 21:42 UTCEG score recompute
2026-10-24 16:29 UTCEPSS rescoreEPSS 0.2% · 13th percentile
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2026-10-18 08:49 UTCEG score recompute
2026-10-17 16:29 UTCEPSS rescoreEPSS 0.2% · 13th percentile
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2026-10-12 19:05 UTCEG score recompute

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2026-10-12 16:30 UTCEPSS rescoreEPSS 0.2% · 13th percentile
2026-10-11 23:31 UTCEG score recompute
2026-10-11 13:44 UTCEPSS rescoreEPSS 0.2% · 13th percentile
2026-10-10 23:17 UTCOSV refresh
2026-10-10 19:56 UTCEPSS rescoreEPSS 0.2% · 13th percentile
2026-10-09 20:04 UTCEPSS rescoreEPSS 0.2% · 13th percentile
2026-10-08 16:40 UTCEPSS rescoreEPSS 0.2% · 13th percentile
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2026-09-30 15:45 UTCEG score recompute
2026-09-30 15:00 UTCEPSS rescoreEPSS 0.2% · 13th percentile
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2026-09-28 13:47 UTCEPSS rescoreEPSS 0.2% · 13th percentile
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2026-09-23 13:45 UTCEPSS rescoreEPSS 0.2% · 14th percentile
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2026-09-21 20:28 UTCEPSS rescoreEPSS 0.2% · 14th percentile
2026-09-21 11:19 UTCOSV refresh
2026-09-20 20:13 UTCEPSS rescoreEPSS 0.2% · 14th percentile
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2026-09-02 14:09 UTCEPSS rescoreEPSS 0.2% · 14th percentile
2026-09-02 09:14 UTCOSV refresh
2026-09-01 13:51 UTCEPSS rescoreEPSS 0.2% · 14th percentile
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2026-08-21 23:46 UTCEPSS rescoreEPSS 0.2% · 14th percentile
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2026-08-16 14:53 UTCEPSS rescoreEPSS 0.2% · 14th percentile
2026-08-16 07:58 UTCOSV refresh
2026-08-16 02:11 UTCEPSS rescoreEPSS 0.2% · 14th percentile
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2026-08-01 04:13 UTCEPSS rescoreEPSS 0.2% · 14th percentile
2026-08-01 01:42 UTCOSV refresh

Same CWE

10 shown

CWE-476

Frequently asked(5)

What is CVE-2021-47540?

CVE-2021-47540 is a medium-severity vulnerability; its CVE record was published on May 24, 2024. In the Linux kernel, the following vulnerability has been resolved: mt76: mt7915: fix NULL pointer dereference in mt7915_get_phy_mode Fix the following NULL pointer dereference in mt7915_get_phy_mode routine adding an ibss interface to the mt7915 driver. [ 101.137097] wlan0: Trigger new scan to…

When was the CVE record for CVE-2021-47540 published?

The CVE record for CVE-2021-47540 was published on May 24, 2024. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of November 21, 2024; the record at its source may have been updated since.

Is CVE-2021-47540 actively exploited?

CVE-2021-47540 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.2% probability of exploitation in the next 30 days (14th percentile of EPSS-scored CVEs).

What is the CVSS score of CVE-2021-47540?

CVE-2021-47540 has a CVSS v3 base score of 5.5 (NVD).

How do I remediate CVE-2021-47540?

A fix for CVE-2021-47540 is available: update to the fixed version the vendor names in its advisory.

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CVE-2021-47540

📅 Published

🔄 Last Modified

🔗 References (3)