CVE-2021-47303

Kernel privilege escalation via BPF use-after-free

Published May 21, 2024 · Updated Aug 5, 2026

Use-after-free in BPF program-array poke tracking in Linux allows local users to gain kernel privileges through BPF system calls. A released subprogram leaves its freed auxiliary poke table tracked by a map, and a later map update dereferences attacker-influenced stale descriptors. The path requires CAP_BPF and can disclose or modify kernel memory, hijack control flow, or panic the host without user interaction.

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 BPF program-array poke tracking in Linux allows local users to gain kernel privileges through BPF system calls. A released subprogram leaves its freed auxiliary poke table tracked by a map, and a later map update dereferences attacker-influenced stale descriptors. The path requires CAP_BPF and can disclose or modify kernel memory, hijack control flow, or panic the host without user interaction.

The record

CVE
CVE-2021-47303
Published
May 21, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-416, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 21, 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=5.10
  2. Affected versionversion=a748c6975dea325da540610c2ba9b5f332c603e6 <599148d40366bd5d1d504a3a8fcd65e21107e500
  3. Affected versionversion=a748c6975dea325da540610c2ba9b5f332c603e6 <a9f36bf3613c65cb587c70fac655c775d911409b
  4. Affected versionversion=a748c6975dea325da540610c2ba9b5f332c603e6 <f263a81451c12da5a342d90572e317e611846f2c

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.10; version=a748c6975dea325da540610c2ba9b5f332c603e6 <599148d40366bd5d1d504a3a8fcd65e21107e500; version=a748c6975dea325da540610c2ba9b5f332c603e6 <a9f36bf3613c65cb587c70fac655c775d911409b; version=a748c6975dea325da540610c2ba9b5f332c603e6 <f263a81451c12da5a342d90572e317e611846f2c

Published CVSS scores

7.8NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
5.5SUSECVSS: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 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

CWE-416Use After Free
T1068Exploitation for Privilege Escalation

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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