CVE-2021-47275

Kernel panic via oversized cache-miss sector count

Published May 21, 2024 · Updated May 11, 2026

Integer truncation in bcache in Linux 3.10 through 5.12.10 allows attackers to crash the kernel through an oversized cache-miss read. cache_lookup_fn() passes a sector count based on an unchecked B+ tree distance to cached_dev_cache_miss(), where the 16-bit bkey size wraps to zero or drives an oversized bio allocation. The path requires a cache miss on a configured bcache cached device, and either resulting guard failure causes a kernel panic and service interruption.

CVSS severityUnavailable
Unscored
EPSS probability0.20%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Integer truncation in bcache in Linux 3.10 through 5.12.10 allows attackers to crash the kernel through an oversized cache-miss read. cache_lookup_fn() passes a sector count based on an unchecked B+ tree distance to cached_dev_cache_miss(), where the 16-bit bkey size wraps to zero or drives an oversized bio allocation. The path requires a cache miss on a configured bcache cached device, and either resulting guard failure causes a kernel panic and service interruption.

The record

CVE
CVE-2021-47275
Published
May 21, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499.004
Attack vector
local
Privileges
Unavailable

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=3.10
  2. Affected versionversion=cafe563591446cf80bfbc2fe3bc72a2e36cf1060 <41fe8d088e96472f63164e213de44ec77be69478
  3. Affected versionversion=cafe563591446cf80bfbc2fe3bc72a2e36cf1060 <555002a840ab88468e252b0eedf0b05e2ce7099c

What conditions does exploitation require?

Attack vectorlocal
Required privilegesUnavailable in this record.

What is affected?

The Linux Kernel Organization · Linuxversion=3.10; version=cafe563591446cf80bfbc2fe3bc72a2e36cf1060 <41fe8d088e96472f63164e213de44ec77be69478; version=cafe563591446cf80bfbc2fe3bc72a2e36cf1060 <555002a840ab88468e252b0eedf0b05e2ce7099c

Published CVSS scores

No CVSS assessment is available in this record.

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
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499.004Endpoint Denial of Service: Application 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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