CVE-2021-46991

Unspecified impact via freed client-instance dereference

Published Feb 28, 2024 · Updated May 11, 2026

Use-after-free in the Linux i40e network driver from 4.16 allows attackers to cause unspecified impact during client-instance cleanup. In i40e_client_subtask(), i40e_client_del_instance() frees pf->cinst, but execution continues and dereferences pf->cinst->lan_info because the function omits a return. Exposure requires the i40e driver and the client-instance deletion path; the Linux CNA has not published a more specific security consequence.

CVSS severity7.8
High
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

Use-after-free in the Linux i40e network driver from 4.16 allows attackers to cause unspecified impact during client-instance cleanup. In i40e_client_subtask(), i40e_client_del_instance() frees pf->cinst, but execution continues and dereferences pf->cinst->lan_info because the function omits a return. Exposure requires the i40e driver and the client-instance deletion path; the Linux CNA has not published a more specific security consequence.

The record

CVE
CVE-2021-46991
Published
Feb 28, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
Unavailable
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 28, 2024CVE publishedPublication date reported by the CVE source.
  2. May 11, 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=4.16
  2. Affected versionversion=7b0b1a6d0ac983ce1928432285d0222d4fb7c38b <1fd5d262e7442192ac7611ff1597a36c5b044323
  3. Affected versionversion=7b0b1a6d0ac983ce1928432285d0222d4fb7c38b <38318f23a7ef86a8b1862e5e8078c4de121960c3
  4. Affected versionversion=7b0b1a6d0ac983ce1928432285d0222d4fb7c38b <4ebc10aa7cd17fd9857dedac69600465c9dd16d1
  5. Affected versionversion=7b0b1a6d0ac983ce1928432285d0222d4fb7c38b <829a713450b8fb127cbabfc1244c1d8179ec5107
  6. Affected versionversion=7b0b1a6d0ac983ce1928432285d0222d4fb7c38b <c1322eaeb8af0d8985b5cc5fa759140fa0e57b84
  7. Affected versionversion=7b0b1a6d0ac983ce1928432285d0222d4fb7c38b <d718c15a2bf9ae082d5ae4d177fb19ef23cb4132

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=4.16; version=7b0b1a6d0ac983ce1928432285d0222d4fb7c38b <1fd5d262e7442192ac7611ff1597a36c5b044323; version=7b0b1a6d0ac983ce1928432285d0222d4fb7c38b <38318f23a7ef86a8b1862e5e8078c4de121960c3; version=7b0b1a6d0ac983ce1928432285d0222d4fb7c38b <4ebc10aa7cd17fd9857dedac69600465c9dd16d1; version=7b0b1a6d0ac983ce1928432285d0222d4fb7c38b <829a713450b8fb127cbabfc1244c1d8179ec5107; version=7b0b1a6d0ac983ce1928432285d0222d4fb7c38b <c1322eaeb8af0d8985b5cc5fa759140fa0e57b84; version=7b0b1a6d0ac983ce1928432285d0222d4fb7c38b <d718c15a2bf9ae082d5ae4d177fb19ef23cb4132

Published CVSS scores

7.8CanonicalCVSS: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

No sourced classifications are available.

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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