CVE-2021-47248

System crash via UDP socket destruction race

Published May 21, 2024 · Updated Aug 5, 2026

Race condition in Linux kernel UDP handling allows local users to crash the system by racing socket destruction against close(). The udp_abort() path can proceed after udp_destroy_sock() or udpv6_destroy_sock() releases the socket lock, rehashing a socket as close() destroys it and leaving a dangling UDP hash node. Exploitation requires concurrent close() and netlink SOCK_DESTROY operations plus CAP_NET_ADMIN in the socket's network namespace; successful triggering causes a kernel panic.

CVSS severity4.7
Medium
EPSS probability0.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Race condition in Linux kernel UDP handling allows local users to crash the system by racing socket destruction against close(). The udp_abort() path can proceed after udp_destroy_sock() or udpv6_destroy_sock() releases the socket lock, rehashing a socket as close() destroys it and leaving a dangling UDP hash node. Exploitation requires concurrent close() and netlink SOCK_DESTROY operations plus CAP_NET_ADMIN in the socket's network namespace; successful triggering causes a kernel panic.

The record

CVE
CVE-2021-47248
Published
May 21, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-362, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 21, 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=5d77dca82839ef016a93ad7acd7058b14d967752 <2f73448041bd0682d4b552cfd314ace66107f1ad
  3. Affected versionversion=5d77dca82839ef016a93ad7acd7058b14d967752 <5a88477c1c85e4baa51e91f2d40f2166235daa56
  4. Affected versionversion=5d77dca82839ef016a93ad7acd7058b14d967752 <65310b0aff86980a011c7c7bfa487a333d4ca241
  5. Affected versionversion=5d77dca82839ef016a93ad7acd7058b14d967752 <8729ec8a2238152a4afc212a331a6cd2c61aeeac
  6. Affected versionversion=5d77dca82839ef016a93ad7acd7058b14d967752 <a0882f68f54f7a8b6308261acee9bd4faab5a69e
  7. Affected versionversion=5d77dca82839ef016a93ad7acd7058b14d967752 <a8b897c7bcd47f4147d066e22cc01d1026d7640e
  8. Affected versionversion=5d77dca82839ef016a93ad7acd7058b14d967752 <e3c36c773aed0fef8b1d3d555b43393ec564400f

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=4.9; version=5d77dca82839ef016a93ad7acd7058b14d967752 <2f73448041bd0682d4b552cfd314ace66107f1ad; version=5d77dca82839ef016a93ad7acd7058b14d967752 <5a88477c1c85e4baa51e91f2d40f2166235daa56; version=5d77dca82839ef016a93ad7acd7058b14d967752 <65310b0aff86980a011c7c7bfa487a333d4ca241; version=5d77dca82839ef016a93ad7acd7058b14d967752 <8729ec8a2238152a4afc212a331a6cd2c61aeeac; version=5d77dca82839ef016a93ad7acd7058b14d967752 <a0882f68f54f7a8b6308261acee9bd4faab5a69e; version=5d77dca82839ef016a93ad7acd7058b14d967752 <a8b897c7bcd47f4147d066e22cc01d1026d7640e; version=5d77dca82839ef016a93ad7acd7058b14d967752 <e3c36c773aed0fef8b1d3d555b43393ec564400f

Published CVSS scores

4.7UbuntuCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
4.7NIST NVDCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
8.8Linux Kernel CNACVSS:3.1/AV:L/AC:L/PR:L/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.

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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-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
T1499.004Application 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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