CVE-2021-47119

Memory leak via unreleased ext4 buffer heads

Published Mar 15, 2024 · Updated May 11, 2026

Memory leak in the Linux kernel ext4 filesystem allows local users to consume kernel memory by repeatedly mounting and unmounting a volume. In ext4_fill_super, a block-size mismatch makes sb_set_blocksize call kill_bdev before buffer-head references are released, leaving the buffer head and its b_data page busy and unfreed. Reaching the leak requires authority to start and stop an ext4 mount; repetition accumulates unreclaimed memory, amplified by dying systemd memory cgroups.

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

Memory leak in the Linux kernel ext4 filesystem allows local users to consume kernel memory by repeatedly mounting and unmounting a volume. In ext4_fill_super, a block-size mismatch makes sb_set_blocksize call kill_bdev before buffer-head references are released, leaving the buffer head and its b_data page busy and unfreed. Reaching the leak requires authority to start and stop an ext4 mount; repetition accumulates unreclaimed memory, amplified by dying systemd memory cgroups.

The record

CVE
CVE-2021-47119
Published
Mar 15, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-401, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 15, 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=2.6.19
  2. Affected versionversion=ac27a0ec112a089f1a5102bc8dffc79c8c815571 <01d349a481f0591230300a9171330136f9159bcd
  3. Affected versionversion=ac27a0ec112a089f1a5102bc8dffc79c8c815571 <1385b23396d511d5233b8b921ac3058b3f86a5e1
  4. Affected versionversion=ac27a0ec112a089f1a5102bc8dffc79c8c815571 <afd09b617db3786b6ef3dc43e28fe728cfea84df

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=2.6.19; version=ac27a0ec112a089f1a5102bc8dffc79c8c815571 <01d349a481f0591230300a9171330136f9159bcd; version=ac27a0ec112a089f1a5102bc8dffc79c8c815571 <1385b23396d511d5233b8b921ac3058b3f86a5e1; version=ac27a0ec112a089f1a5102bc8dffc79c8c815571 <afd09b617db3786b6ef3dc43e28fe728cfea84df

Published CVSS scores

5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
4.1Amazon LinuxCVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H
5.5UbuntuCVSS: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 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-401Missing Release of Memory after Effective Lifetime
T1499Endpoint Denial of Service

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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