CVE-2021-46911

Kernel panic via kTLS transmit race

Published Feb 27, 2024 · Updated Aug 5, 2026

Use-after-free in Chelsio kTLS transmit handling in Linux 5.7 and affected stable branches allows local users to trigger a kernel panic. The transmit path takes page references without holding the transmit-context lock, allowing an ACK to free a TLS record while it is copied. Exploitation requires local low-privileged access and the Chelsio kTLS-offload path; the bounded consequence is a host crash, not data disclosure or modification.

CVSS severity5.5
Medium
EPSS probability0.59%
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 Chelsio kTLS transmit handling in Linux 5.7 and affected stable branches allows local users to trigger a kernel panic. The transmit path takes page references without holding the transmit-context lock, allowing an ACK to free a TLS record while it is copied. Exploitation requires local low-privileged access and the Chelsio kTLS-offload path; the bounded consequence is a host crash, not data disclosure or modification.

The record

CVE
CVE-2021-46911
Published
Feb 27, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499
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=5.7
  2. Affected versionversion=5a4b9fe7fece62ecab6fb28fe92362f83b41c33e <1a73e427b824133940c2dd95ebe26b6dce1cbf10
  3. Affected versionversion=5a4b9fe7fece62ecab6fb28fe92362f83b41c33e <8348665d4181c68b0ca1205b48e1753d78bc810f
  4. Affected versionversion=5a4b9fe7fece62ecab6fb28fe92362f83b41c33e <8d5a9dbd2116a852f8f0f91f6fbc42a0afe1091f

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.7; version=5a4b9fe7fece62ecab6fb28fe92362f83b41c33e <1a73e427b824133940c2dd95ebe26b6dce1cbf10; version=5a4b9fe7fece62ecab6fb28fe92362f83b41c33e <8348665d4181c68b0ca1205b48e1753d78bc810f; version=5a4b9fe7fece62ecab6fb28fe92362f83b41c33e <8d5a9dbd2116a852f8f0f91f6fbc42a0afe1091f

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.

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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

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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