CVE-2021-47238

Service interruption via unreleased IGMP source lists

Published May 21, 2024 · Updated May 23, 2026

Memory leak in Linux kernel IPv4 IGMP handling allows local users to consume kernel memory through repeated multicast source operations. During interface teardown, ip_mc_destroy_dev omits ip_mc_clear_src before clearing dev->ip_ptr, leaving mc_list source allocations unreachable by socket-close cleanup. Low-privileged local access is required, and repeated triggering can exhaust memory and interrupt service.

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

Memory leak in Linux kernel IPv4 IGMP handling allows local users to consume kernel memory through repeated multicast source operations. During interface teardown, ip_mc_destroy_dev omits ip_mc_clear_src before clearing dev->ip_ptr, leaving mc_list source allocations unreachable by socket-close cleanup. Low-privileged local access is required, and repeated triggering can exhaust memory and interrupt service.

The record

CVE
CVE-2021-47238
Published
May 21, 2024
Updated
May 23, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-400, T1499.001
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 21, 2024CVE publishedPublication date reported by the CVE source.
  2. May 23, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=24803f38a5c0b6c57ed800b47e695f9ce474bc3a <0dc13e75507faa17ac9f7562b4ef7bf8fcd78422
  2. Affected versionversion=24803f38a5c0b6c57ed800b47e695f9ce474bc3a <1e28018b5c83d5073f74a6fb72eabe8370b2f501
  3. Affected versionversion=24803f38a5c0b6c57ed800b47e695f9ce474bc3a <3dd2aeac2e9624cff9fa634710837e4f2e352758
  4. Affected versionversion=24803f38a5c0b6c57ed800b47e695f9ce474bc3a <6cff57eea3347f79f1867cc53e1093b6614138d8
  5. Affected versionversion=24803f38a5c0b6c57ed800b47e695f9ce474bc3a <77de6ee73f54a9a89c0afa0bf4c53b239aa9953a
  6. Affected versionversion=24803f38a5c0b6c57ed800b47e695f9ce474bc3a <ac31cc837cafb57a271babad8ccffbf733caa076
  7. Affected versionversion=24803f38a5c0b6c57ed800b47e695f9ce474bc3a <d8e2973029b8b2ce477b564824431f3385c77083
  8. Affected versionversion=3.16.42 <3.17
  9. Affected versionversion=3.2.87 <3.3
  10. Affected versionversion=4.9
  11. Affected versionversion=b38c6e0bd5b5e439ecebdc0df599d573c2f610f8
  12. Affected versionversion=bd1b664a19403ede448d29c87b2f23796bc7a577

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=24803f38a5c0b6c57ed800b47e695f9ce474bc3a <0dc13e75507faa17ac9f7562b4ef7bf8fcd78422; version=24803f38a5c0b6c57ed800b47e695f9ce474bc3a <1e28018b5c83d5073f74a6fb72eabe8370b2f501; version=24803f38a5c0b6c57ed800b47e695f9ce474bc3a <3dd2aeac2e9624cff9fa634710837e4f2e352758; version=24803f38a5c0b6c57ed800b47e695f9ce474bc3a <6cff57eea3347f79f1867cc53e1093b6614138d8; version=24803f38a5c0b6c57ed800b47e695f9ce474bc3a <77de6ee73f54a9a89c0afa0bf4c53b239aa9953a; version=24803f38a5c0b6c57ed800b47e695f9ce474bc3a <ac31cc837cafb57a271babad8ccffbf733caa076; version=24803f38a5c0b6c57ed800b47e695f9ce474bc3a <d8e2973029b8b2ce477b564824431f3385c77083; version=3.16.42 <3.17; version=3.2.87 <3.3; version=4.9; version=b38c6e0bd5b5e439ecebdc0df599d573c2f610f8; version=bd1b664a19403ede448d29c87b2f23796bc7a577
The Linux Kernel Organization · Linux Kernelversion=24803f38a5c0 <0dc13e75507f; version=24803f38a5c0 <1e28018b5c83; version=24803f38a5c0 <3dd2aeac2e96; version=24803f38a5c0 <6cff57eea334; version=24803f38a5c0 <77de6ee73f54; version=24803f38a5c0 <ac31cc837caf; version=24803f38a5c0 <d8e2973029b8; version=4.9

Published CVSS scores

5.5CISA-ADPCVSS: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 exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499.001OS Exhaustion Flood

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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