CVE-2021-47013Network attack vector

Kernel memory corruption via freed transmit buffer

Published Feb 28, 2024 · Updated Aug 5, 2026

Use-after-free in the Qualcomm EMAC transmit path in affected Linux kernels allows remote attackers to corrupt memory via network traffic. An EMAC transmit error causes emac_tx_fill_tpd to free the socket buffer, but emac_mac_tx_buf_send then reads skb->len and passes it to netdev_sent_queue. Reachability requires the Qualcomm EMAC driver and traffic that induces a DMA mapping failure; consequences include kernel memory disclosure or corruption, transmit-queue stall, and crash.

CVSS severity9.8
Critical
EPSS probability0.78%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in the Qualcomm EMAC transmit path in affected Linux kernels allows remote attackers to corrupt memory via network traffic. An EMAC transmit error causes emac_tx_fill_tpd to free the socket buffer, but emac_mac_tx_buf_send then reads skb->len and passes it to netdev_sent_queue. Reachability requires the Qualcomm EMAC driver and traffic that induces a DMA mapping failure; consequences include kernel memory disclosure or corruption, transmit-queue stall, and crash.

The record

CVE
CVE-2021-47013
Published
Feb 28, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-416, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 28, 2024CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=4.9
  2. Affected versionversion=b9b17debc69d27cd55e21ee51a5ba7fc50a426cf <16d8c44be52e3650917736d45f5904384a9da834
  3. Affected versionversion=b9b17debc69d27cd55e21ee51a5ba7fc50a426cf <55fcdd1258faaecca74b91b88cc0921f9edd775d
  4. Affected versionversion=b9b17debc69d27cd55e21ee51a5ba7fc50a426cf <6d72e7c767acbbdd44ebc7d89c6690b405b32b57
  5. Affected versionversion=b9b17debc69d27cd55e21ee51a5ba7fc50a426cf <8c06f34785068b87e2b560534c77c163d6c6dca7
  6. Affected versionversion=b9b17debc69d27cd55e21ee51a5ba7fc50a426cf <9dc373f74097edd0e35f3393d6248eda8d1ba99d
  7. Affected versionversion=b9b17debc69d27cd55e21ee51a5ba7fc50a426cf <c7f75d11fe72913d2619f97b2334b083cd7bb955
  8. Affected versionversion=b9b17debc69d27cd55e21ee51a5ba7fc50a426cf <dc1b438a35773d030be0ee80d9c635c3e558a322
  9. Affected versionversion=b9b17debc69d27cd55e21ee51a5ba7fc50a426cf <e407495ba6788a67d1bd41714158c079e340879b

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=4.9; version=b9b17debc69d27cd55e21ee51a5ba7fc50a426cf <16d8c44be52e3650917736d45f5904384a9da834; version=b9b17debc69d27cd55e21ee51a5ba7fc50a426cf <55fcdd1258faaecca74b91b88cc0921f9edd775d; version=b9b17debc69d27cd55e21ee51a5ba7fc50a426cf <6d72e7c767acbbdd44ebc7d89c6690b405b32b57; version=b9b17debc69d27cd55e21ee51a5ba7fc50a426cf <8c06f34785068b87e2b560534c77c163d6c6dca7; version=b9b17debc69d27cd55e21ee51a5ba7fc50a426cf <9dc373f74097edd0e35f3393d6248eda8d1ba99d; version=b9b17debc69d27cd55e21ee51a5ba7fc50a426cf <c7f75d11fe72913d2619f97b2334b083cd7bb955; version=b9b17debc69d27cd55e21ee51a5ba7fc50a426cf <dc1b438a35773d030be0ee80d9c635c3e558a322; version=b9b17debc69d27cd55e21ee51a5ba7fc50a426cf <e407495ba6788a67d1bd41714158c079e340879b

Published CVSS scores

7.8NISTCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
9.8kernel.orgCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-416Use After Free
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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