CVE-2021-47175

Local privilege escalation via fq_pie flow indexing

Published Mar 25, 2024 · Updated Aug 5, 2026

Out-of-bounds access in the Linux kernel fq_pie scheduler allows local users to corrupt kernel memory through crafted packet metadata. fq_pie_qdisc_enqueue accepts a flow index equal to flows_cnt and dereferences the object immediately beyond the allocated q->flows array. CAP_NET_ADMIN in a user namespace is sufficient; the resulting reads, writes, and list corruption enable disclosure, privilege escalation, or a kernel panic.

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 Linux kernel fq_pie scheduler allows local users to corrupt kernel memory through crafted packet metadata. fq_pie_qdisc_enqueue accepts a flow index equal to flows_cnt and dereferences the object immediately beyond the allocated q->flows array. CAP_NET_ADMIN in a user namespace is sufficient; the resulting reads, writes, and list corruption enable disclosure, privilege escalation, or a kernel panic.

The record

CVE
CVE-2021-47175
Published
Mar 25, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-125, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 25, 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=5.6
  2. Affected versionversion=ec97ecf1ebe485a17cd8395a5f35e6b80b57665a <7a1bdec12e43e29cc34a4394590337069d8812ce
  3. Affected versionversion=ec97ecf1ebe485a17cd8395a5f35e6b80b57665a <e6294c06e7c62ffdd5bf3df696d3a4fcbb753d3c
  4. Affected versionversion=ec97ecf1ebe485a17cd8395a5f35e6b80b57665a <e70f7a11876a1a788ceadf75e9e5f7af2c868680

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.6; version=ec97ecf1ebe485a17cd8395a5f35e6b80b57665a <7a1bdec12e43e29cc34a4394590337069d8812ce; version=ec97ecf1ebe485a17cd8395a5f35e6b80b57665a <e6294c06e7c62ffdd5bf3df696d3a4fcbb753d3c; version=ec97ecf1ebe485a17cd8395a5f35e6b80b57665a <e70f7a11876a1a788ceadf75e9e5f7af2c868680

Published CVSS scores

7.1NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
7.1Amazon LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
8.8Linux kernel CVE teamCVSS: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

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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