CVE-2021-47300

Kernel freeze or corruption via unpropagated BPF flag

Published May 21, 2024 · Updated Aug 5, 2026

Out-of-bounds access in the BPF verifier in affected Linux 5.10 through 5.13 branches allows local users to freeze or corrupt the kernel. check_max_stack_depth() updates each subprogram's tail_call_reachable flag but fails to propagate the main program's value to env->prog->aux, so JIT failure leaves an invalid BPF-to-BPF tail-call program eligible for interpreter execution. The path requires CAP_BPF or CAP_SYS_ADMIN and a crafted program that forces JIT allocation failure; execution can recurse until kernel stack overflow, memory corruption, crash, or freeze occurs.

CVSS severity8.8
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

Out-of-bounds access in the BPF verifier in affected Linux 5.10 through 5.13 branches allows local users to freeze or corrupt the kernel. check_max_stack_depth() updates each subprogram's tail_call_reachable flag but fails to propagate the main program's value to env->prog->aux, so JIT failure leaves an invalid BPF-to-BPF tail-call program eligible for interpreter execution. The path requires CAP_BPF or CAP_SYS_ADMIN and a crafted program that forces JIT allocation failure; execution can recurse until kernel stack overflow, memory corruption, crash, or freeze occurs.

The record

CVE
CVE-2021-47300
Published
May 21, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-125, T1068, T1499.004
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

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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=5.10
  2. Affected versionversion=ebf7d1f508a73871acf3b2bfbfa1323a477acdb3 <39f1735c8107ef43a53c4daf82f330d880488d8f
  3. Affected versionversion=ebf7d1f508a73871acf3b2bfbfa1323a477acdb3 <5dd0a6b8582ffbfa88351949d50eccd5b6694ade
  4. Affected versionversion=ebf7d1f508a73871acf3b2bfbfa1323a477acdb3 <cbb086074dab631ac43f8645cbac1d7b148e05c4

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.10; version=ebf7d1f508a73871acf3b2bfbfa1323a477acdb3 <39f1735c8107ef43a53c4daf82f330d880488d8f; version=ebf7d1f508a73871acf3b2bfbfa1323a477acdb3 <5dd0a6b8582ffbfa88351949d50eccd5b6694ade; version=ebf7d1f508a73871acf3b2bfbfa1323a477acdb3 <cbb086074dab631ac43f8645cbac1d7b148e05c4

Published CVSS scores

5.5NIST National Vulnerability DatabaseCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
6.0SUSECVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:H
8.8Linux kernel CNACVSS: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

CWE-125Out-of-bounds Read
T1068Exploitation for Privilege Escalation
T1499.004Application or System Exploitation

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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