CVE-2021-47146Public exploit

Local kernel panic via oversized MLD headroom

Published Mar 25, 2024 · Updated May 11, 2026

Denial of service in the Linux kernel allows local users to trigger a kernel panic through crafted nested IPv6 GRE tunnel setup. The mld_newpack function permits only an order-0 socket-buffer allocation even when nested IPv6 tunnel headers make the required headroom exceed one page, so skb_put reaches a kernel BUG. Exploitation requires local low-privileged access sufficient to configure the demonstrated network namespaces and nested IPv6 GRE tunnels; the resulting impact is a host crash.

CVSS severity5.5
Medium
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in the Linux kernel allows local users to trigger a kernel panic through crafted nested IPv6 GRE tunnel setup. The mld_newpack function permits only an order-0 socket-buffer allocation even when nested IPv6 tunnel headers make the required headroom exceed one page, so skb_put reaches a kernel BUG. Exploitation requires local low-privileged access sufficient to configure the demonstrated network namespaces and nested IPv6 GRE tunnels; the resulting impact is a host crash.

The record

CVE
CVE-2021-47146
Published
Mar 25, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 25, 2024CVE publishedPublication date reported by the CVE source.
  2. May 11, 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=2.6.35
  2. Affected versionversion=72e09ad107e78d69ff4d3b97a69f0aad2b77280f <020ef930b826d21c5446fdc9db80fd72a791bc21
  3. Affected versionversion=72e09ad107e78d69ff4d3b97a69f0aad2b77280f <0e35b7457b7b6e73ffeaaca1a577fdf1af0feca1
  4. Affected versionversion=72e09ad107e78d69ff4d3b97a69f0aad2b77280f <17728616a4c85baf0edc975c60ba4e4157684d9a
  5. Affected versionversion=72e09ad107e78d69ff4d3b97a69f0aad2b77280f <221142038f36d9f28b64e83e954774da4d4ccd17
  6. Affected versionversion=72e09ad107e78d69ff4d3b97a69f0aad2b77280f <37d697759958d111439080bab7e14d2b0e7b39f5
  7. Affected versionversion=72e09ad107e78d69ff4d3b97a69f0aad2b77280f <4b77ad9097067b31237eeeee0bf70f80849680a0
  8. Affected versionversion=72e09ad107e78d69ff4d3b97a69f0aad2b77280f <a76fb9ba545289379acf409653ad5f74417be59c
  9. Affected versionversion=72e09ad107e78d69ff4d3b97a69f0aad2b77280f <beb39adb150f8f3b516ddf7c39835a9788704d23

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=2.6.35; version=72e09ad107e78d69ff4d3b97a69f0aad2b77280f <020ef930b826d21c5446fdc9db80fd72a791bc21; version=72e09ad107e78d69ff4d3b97a69f0aad2b77280f <0e35b7457b7b6e73ffeaaca1a577fdf1af0feca1; version=72e09ad107e78d69ff4d3b97a69f0aad2b77280f <17728616a4c85baf0edc975c60ba4e4157684d9a; version=72e09ad107e78d69ff4d3b97a69f0aad2b77280f <221142038f36d9f28b64e83e954774da4d4ccd17; version=72e09ad107e78d69ff4d3b97a69f0aad2b77280f <37d697759958d111439080bab7e14d2b0e7b39f5; version=72e09ad107e78d69ff4d3b97a69f0aad2b77280f <4b77ad9097067b31237eeeee0bf70f80849680a0; version=72e09ad107e78d69ff4d3b97a69f0aad2b77280f <a76fb9ba545289379acf409653ad5f74417be59c; version=72e09ad107e78d69ff4d3b97a69f0aad2b77280f <beb39adb150f8f3b516ddf7c39835a9788704d23

Published CVSS scores

5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5UbuntuCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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.

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No observations available

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

Weakness, pattern, technique

T1499Endpoint Denial of Service

Public exploit references

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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