CVE-2021-47215

Kernel crash via unprotected kTLS resync list

Published Apr 10, 2024 · Updated Aug 5, 2026

A race in Linux kernel 5.13 through 5.15.4 allows local users to crash the system through mlx5e kTLS receive resynchronization. resync_handle_seq_match() could move a TLS context list entry while NAPI was still processing it because access lacked per-context locking. The path requires low-privilege local access, Mellanox mlx5 hardware, and kTLS receive offload; the documented consequence is a kernel crash.

CVSS severity5.5
Medium
EPSS probability0.49%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

A race in Linux kernel 5.13 through 5.15.4 allows local users to crash the system through mlx5e kTLS receive resynchronization. resync_handle_seq_match() could move a TLS context list entry while NAPI was still processing it because access lacked per-context locking. The path requires low-privilege local access, Mellanox mlx5 hardware, and kTLS receive offload; the documented consequence is a kernel crash.

The record

CVE
CVE-2021-47215
Published
Apr 10, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 10, 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=5.13
  2. Affected versionversion=e9ce991bce5bacf71641bd0f72f4b7c589529f40 <cc4a9cc03faa6d8db1a6954bb536f2c1e63bdff6
  3. Affected versionversion=e9ce991bce5bacf71641bd0f72f4b7c589529f40 <ebeda7a9528ae690e6bf12791a868f0cca8391f2

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.13; version=e9ce991bce5bacf71641bd0f72f4b7c589529f40 <cc4a9cc03faa6d8db1a6954bb536f2c1e63bdff6; version=e9ce991bce5bacf71641bd0f72f4b7c589529f40 <ebeda7a9528ae690e6bf12791a868f0cca8391f2

Published CVSS scores

5.5NIST NVDCVSS: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.

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)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499Endpoint Denial of Service

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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