CVE-2021-47563

Kernel crash via XDP reference-count underflow

Published May 24, 2024 · Updated May 11, 2026

Use-after-free in the Linux ice network driver allows local users to crash the kernel during an XDP-enabled VSI rebuild. ice_prepare_xdp_rings passes vsi->xdp_prog to ice_vsi_assign_bpf_prog, which treats the identical pointer as the old program and calls bpf_prog_put, dropping its reference count to zero while the kernel still uses it. Reachability requires an ice device with XDP active and local ability to rebuild the VSI, such as by changing interface queue counts; the observed consequence is a kernel page fault and service interruption.

CVSS severity5.5
Medium
EPSS probability0.21%
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 ice network driver allows local users to crash the kernel during an XDP-enabled VSI rebuild. ice_prepare_xdp_rings passes vsi->xdp_prog to ice_vsi_assign_bpf_prog, which treats the identical pointer as the old program and calls bpf_prog_put, dropping its reference count to zero while the kernel still uses it. Reachability requires an ice device with XDP active and local ability to rebuild the VSI, such as by changing interface queue counts; the observed consequence is a kernel page fault and service interruption.

The record

CVE
CVE-2021-47563
Published
May 24, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1529
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 24, 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=5.5
  2. Affected versionversion=efc2214b6047b6f5b4ca53151eba62521b9452d6 <1f10b09ccc832698ef4624a6ab9a213b6ccbda76
  3. Affected versionversion=efc2214b6047b6f5b4ca53151eba62521b9452d6 <e65a8707b4cd756d26d246bb2b9fab06eebafac1
  4. Affected versionversion=efc2214b6047b6f5b4ca53151eba62521b9452d6 <f65ee535df775a13a1046c0a0b2d72db342f8a5b

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.5; version=efc2214b6047b6f5b4ca53151eba62521b9452d6 <1f10b09ccc832698ef4624a6ab9a213b6ccbda76; version=efc2214b6047b6f5b4ca53151eba62521b9452d6 <e65a8707b4cd756d26d246bb2b9fab06eebafac1; version=efc2214b6047b6f5b4ca53151eba62521b9452d6 <f65ee535df775a13a1046c0a0b2d72db342f8a5b

Published CVSS scores

5.5CISA-ADPCVSS: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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1529System Shutdown/Reboot

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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