CVE-2021-47376

Kernel warning via oversized BPF line information

Published May 21, 2024 · Updated May 11, 2026

Improper input validation in affected Linux 5.x kernels allows local users to trigger a kernel warning with oversized BPF line data. The BPF verifier's check_btf_line function passes line_info_cnt to kvcalloc without first rejecting counts above INT_MAX divided by the record size. A local user able to submit BPF program metadata can reach the allocation path, with the documented consequence limited to availability impact and a warning.

CVSS severity5.5
Medium
EPSS probability0.25%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in affected Linux 5.x kernels allows local users to trigger a kernel warning with oversized BPF line data. The BPF verifier's check_btf_line function passes line_info_cnt to kvcalloc without first rejecting counts above INT_MAX divided by the record size. A local user able to submit BPF program metadata can reach the allocation path, with the documented consequence limited to availability impact and a warning.

The record

CVE
CVE-2021-47376
Published
May 21, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 21, 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=5.0
  2. Affected versionversion=c454a46b5efd8eff8880e88ece2976e60a26bf35 <0e6491b559704da720f6da09dd0a52c4df44c514
  3. Affected versionversion=c454a46b5efd8eff8880e88ece2976e60a26bf35 <6345a0bee80139ea00a341c4202ebfd1534b5eb0
  4. Affected versionversion=c454a46b5efd8eff8880e88ece2976e60a26bf35 <93937596e0652d50973f9dc944fea1694ac8cdfd
  5. Affected versionversion=c454a46b5efd8eff8880e88ece2976e60a26bf35 <b5fe7cdfee5901ce5513c30e554d51536e003bde

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.0; version=c454a46b5efd8eff8880e88ece2976e60a26bf35 <0e6491b559704da720f6da09dd0a52c4df44c514; version=c454a46b5efd8eff8880e88ece2976e60a26bf35 <6345a0bee80139ea00a341c4202ebfd1534b5eb0; version=c454a46b5efd8eff8880e88ece2976e60a26bf35 <93937596e0652d50973f9dc944fea1694ac8cdfd; version=c454a46b5efd8eff8880e88ece2976e60a26bf35 <b5fe7cdfee5901ce5513c30e554d51536e003bde

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

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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