CVE-2021-47585

Service interruption via unreleased btrfs allocation

Published Jun 19, 2024 · Updated May 11, 2026

A memory leak in btrfs in Linux kernel 5.5 allows local users to exhaust kernel memory through inode-reference replay errors. The __add_inode_ref() error path returns when backref_in_log() fails after kmalloc() allocates victim_name, but it omits the matching kfree(). Repeatedly reaching that local btrfs log-replay path consumes kernel memory and can interrupt service; no confidentiality or integrity impact is reported.

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

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

A memory leak in btrfs in Linux kernel 5.5 allows local users to exhaust kernel memory through inode-reference replay errors. The __add_inode_ref() error path returns when backref_in_log() fails after kmalloc() allocates victim_name, but it omits the matching kfree(). Repeatedly reaching that local btrfs log-replay path consumes kernel memory and can interrupt service; no confidentiality or integrity impact is reported.

The record

CVE
CVE-2021-47585
Published
Jun 19, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-401, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 19, 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

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=5.5
  2. Affected versionversion=d3316c8233bb05e0dd855d30aac347bb8ad76ee4 <005d9292b5b2e71a009f911bd85d755009b37242
  3. Affected versionversion=d3316c8233bb05e0dd855d30aac347bb8ad76ee4 <493ff661d434d6bdf02e3a21adae04d7a0b4265d
  4. Affected versionversion=d3316c8233bb05e0dd855d30aac347bb8ad76ee4 <f35838a6930296fc1988764cfa54cb3f705c0665

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.5; version=d3316c8233bb05e0dd855d30aac347bb8ad76ee4 <005d9292b5b2e71a009f911bd85d755009b37242; version=d3316c8233bb05e0dd855d30aac347bb8ad76ee4 <493ff661d434d6bdf02e3a21adae04d7a0b4265d; version=d3316c8233bb05e0dd855d30aac347bb8ad76ee4 <f35838a6930296fc1988764cfa54cb3f705c0665

Published CVSS scores

5.5NISTCVSS: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 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-401Missing Release of Memory after Effective Lifetime
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

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo