CVE-2021-47103

Kernel compromise via RCU use-after-free

Published Mar 4, 2024 · Updated Aug 5, 2026

Use-after-free in the Linux kernel allows local users to read or alter kernel-managed data or crash the system through affected receive paths. In tcp_v4_do_rcv and tcp_v6_do_rcv, code releases the RCU-protected sk_rx_dst destination before clearing the pointer, allowing early demultiplexing to dereference freed memory. Exploitation requires local low-privileged access and winning the relevant timing window; the demonstrated failure is a KASAN-detected invalid kernel read.

CVSS severity7.8
High
EPSS probability0.95%
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

Use-after-free in the Linux kernel allows local users to read or alter kernel-managed data or crash the system through affected receive paths. In tcp_v4_do_rcv and tcp_v6_do_rcv, code releases the RCU-protected sk_rx_dst destination before clearing the pointer, allowing early demultiplexing to dereference freed memory. Exploitation requires local low-privileged access and winning the relevant timing window; the demonstrated failure is a KASAN-detected invalid kernel read.

The record

CVE
CVE-2021-47103
Published
Mar 4, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-416
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 4, 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

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=3.6
  2. Affected versionversion=41063e9dd11956f2d285e12e4342e1d232ba0ea2 <0249a4b8a554f2eb6a27b62516fa50168584faa4
  3. Affected versionversion=41063e9dd11956f2d285e12e4342e1d232ba0ea2 <68c34ce11ef23328692aa35fa6aaafdd75913100
  4. Affected versionversion=41063e9dd11956f2d285e12e4342e1d232ba0ea2 <75a578000ae5e511e5d0e8433c94a14d9c99c412
  5. Affected versionversion=41063e9dd11956f2d285e12e4342e1d232ba0ea2 <8f905c0e7354ef261360fb7535ea079b1082c105
  6. Affected versionversion=41063e9dd11956f2d285e12e4342e1d232ba0ea2 <92e6e36ecd16808866ac6172b9491b5097cde449
  7. Affected versionversion=41063e9dd11956f2d285e12e4342e1d232ba0ea2 <c3bb4a7e8cbc984e1cdac0fe6af60e880214ed6e
  8. Affected versionversion=41063e9dd11956f2d285e12e4342e1d232ba0ea2 <f039b43cbaea5e0700980c2f0052da05a70782e0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=3.6; version=41063e9dd11956f2d285e12e4342e1d232ba0ea2 <0249a4b8a554f2eb6a27b62516fa50168584faa4; version=41063e9dd11956f2d285e12e4342e1d232ba0ea2 <68c34ce11ef23328692aa35fa6aaafdd75913100; version=41063e9dd11956f2d285e12e4342e1d232ba0ea2 <75a578000ae5e511e5d0e8433c94a14d9c99c412; version=41063e9dd11956f2d285e12e4342e1d232ba0ea2 <8f905c0e7354ef261360fb7535ea079b1082c105; version=41063e9dd11956f2d285e12e4342e1d232ba0ea2 <92e6e36ecd16808866ac6172b9491b5097cde449; version=41063e9dd11956f2d285e12e4342e1d232ba0ea2 <c3bb4a7e8cbc984e1cdac0fe6af60e880214ed6e; version=41063e9dd11956f2d285e12e4342e1d232ba0ea2 <f039b43cbaea5e0700980c2f0052da05a70782e0

Published CVSS scores

7.8NISTCVSS: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.

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-416Use After Free

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