CVE-2021-46925

Kernel panic via SMC socket teardown race

Published Feb 27, 2024 · Updated Aug 5, 2026

Use-after-free in the Linux kernel's SMC networking subsystem allows local users to crash the kernel by racing socket teardown. smc_release() can free smc_sock after smc_cdc_tx_handler() verifies the connection but before it locks and uses the socket. Triggering requires local low-privileged access and an SMC-R path with in-flight CDC work; the resulting page fault produces a kernel panic and service interruption.

CVSS severity4.7
Medium
EPSS probability0.18%
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 Linux kernel's SMC networking subsystem allows local users to crash the kernel by racing socket teardown. smc_release() can free smc_sock after smc_cdc_tx_handler() verifies the connection but before it locks and uses the socket. Triggering requires local low-privileged access and an SMC-R path with in-flight CDC work; the resulting page fault produces a kernel panic and service interruption.

The record

CVE
CVE-2021-46925
Published
Feb 27, 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. Feb 27, 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

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=4.11
  2. Affected versionversion=5f08318f617b05b6ee389d8bd174c7af921ebf19 <349d43127dac00c15231e8ffbcaabd70f7b0e544
  3. Affected versionversion=5f08318f617b05b6ee389d8bd174c7af921ebf19 <b85f751d71ae8e2a15e9bda98852ea9af35282eb
  4. Affected versionversion=5f08318f617b05b6ee389d8bd174c7af921ebf19 <e8a5988a85c719ce7205cb00dcf0716dcf611332

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=4.11; version=5f08318f617b05b6ee389d8bd174c7af921ebf19 <349d43127dac00c15231e8ffbcaabd70f7b0e544; version=5f08318f617b05b6ee389d8bd174c7af921ebf19 <b85f751d71ae8e2a15e9bda98852ea9af35282eb; version=5f08318f617b05b6ee389d8bd174c7af921ebf19 <e8a5988a85c719ce7205cb00dcf0716dcf611332

Published CVSS scores

4.7CISA ADPCVSS:3.1/AV:L/AC:H/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-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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