CVE-2021-47103: In the Linux kernel, the following vulnerability has been resolved: inet: fully convert sk->sk_rx_dst to RCU

Q: How do I fix CVE-2021-47103?

linux kernel: upgrade to 4.9.331, 4.14.296, 4.19.262, 5.4.220, 5.10.150, 5.15.12. Exact commands for each OS are on this page.

Q: Is CVE-2021-47103 being exploited?

CVE-2021-47103 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-47103 affect?

CVE-2021-47103 affects linux kernel. Severity is critical (CVSS 9.8). In the Linux kernel, the following vulnerability has been resolved: inet: fully convert sk->sk_rx_dst to RCU rules syzbot reported various issues around early demux, one being included in this changelog [1] sk->sk_rx_dst is using RCU pro

This week

CRITICAL 9.8REMOTEWATCHLISTUPGRADE

CVE-2021-47103 is a critical-severity flaw (CVSS 9.8) affecting linux kernel. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

In the Linux kernel, the following vulnerability has been resolved: inet: fully convert sk->sk_rx_dst to RCU rules syzbot reported various issues around early demux, one being included in this changelog [1] sk->sk_rx_dst is using RCU protection without clearly documenting it. And following sequences in tcp_v4_do_rcv()/tcp_v6_do_rcv() are not following standard RCU rules. [a] dst_release(dst); [b] sk->sk_rx_dst = NULL; They look wrong

Why this priority

Critical severity
Public exploit reference
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.0% (top 39%)
CISA exploited list	No
Weakness	CWE-416
Published	2024-03-04
Last modified	2026-08-04

Publisher (CNA): kernel.org · Vendor: linux

Last updated 2026-08-04 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2024-03-04 18:15 UTCPublished CVE record published
2026-08-04 10:16 UTCUpdated Record last modified

linux linux kernel UPGRADE

Affected: >= 3.6 and < 4.9.331 · >= 4.10 and < 4.14.296 · >= 4.15 and < 4.19.262 · >= 4.20 and < 5.4.220 · >= 5.5 and < 5.10.150 · >= 5.11 and < 5.15.12 · 5.16 rc1 · 5.16 rc2

Fixed in: 4.9.331, 4.14.296, 4.19.262, 5.4.220, 5.10.150, 5.15.12

Safe to downgrade to: no unaffected older release

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Exact fixes by distribution

Fedora 46 · sbcl · FIXED · 2.6.10-1.fc46 · FEDORA-2026-feab1a81c6 · source

sudo dnf upgrade --advisory=FEDORA-2026-feab1a81c6

Fedora ELN · python-archspec · FIXED · 0.2.7-1.eln159 · FEDORA-2026-e2a8272db6 · source

sudo dnf upgrade --advisory=FEDORA-2026-e2a8272db6

Ubuntu 22.04 · linux · NOT AFFECTED

Ubuntu 24.04 · linux · NOT AFFECTED

Ubuntu 20.04 · linux · FIXED · 5.4.0-139.156

sudo apt update && sudo apt install --only-upgrade linux dpkg --compare-versions "$(dpkg-query -W -f='${Version}' linux)" ge "5.4.0-139.156" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 24.10 · linux · NOT AFFECTED

Ubuntu 25.04 · linux · NOT AFFECTED

Debian 12 · linux · FIXED · 5.15.15-1

sudo apt update && sudo apt install --only-upgrade linux dpkg --compare-versions "$(dpkg-query -W -f='${Version}' linux)" ge "5.15.15-1" && echo PATCHED || echo STILL-VULNERABLE

Debian 13 · linux · FIXED · 5.15.15-1

sudo apt update && sudo apt install --only-upgrade linux dpkg --compare-versions "$(dpkg-query -W -f='${Version}' linux)" ge "5.15.15-1" && echo PATCHED || echo STILL-VULNERABLE

RHEL 8 · kernel · FIXED · kernel-4.18.0-425.3.1.el8

sudo dnf upgrade --advisory=RHSA-2022:7683 rpm -q kernel

RHEL 9 · kernel · FIXED · kernel-5.14.0-162.6.1.el9_1

sudo dnf upgrade --advisory=RHSA-2022:8267 rpm -q kernel

RHEL 6 · kernel · DEFERRED

RHEL 7 · kernel · DEFERRED

RHEL 7 · kernel-rt · DEFERRED

Amazon Linux 2 · see advisory · FIXED · ALAS2-2022-1876 · source

sudo yum update --advisory=ALAS2-2022-1876

Amazon Linux 1 · see advisory · FIXED · ALAS-2022-1645 · source

sudo yum update --advisory=ALAS-2022-1645

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-47103?

linux kernel: upgrade to 4.9.331, 4.14.296, 4.19.262, 5.4.220, 5.10.150, 5.15.12. Exact commands for each OS are on this page.

Is CVE-2021-47103 being exploited?

CVE-2021-47103 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-47103 affect?

CVE-2021-47103 affects linux kernel. Severity is critical (CVSS 9.8). In the Linux kernel, the following vulnerability has been resolved: inet: fully convert sk->sk_rx_dst to RCU rules syzbot reported various issues around early demux, one being included in this changelog [1] sk->sk_rx_dst is using RCU pro

How urgent is CVE-2021-47103?

Priority 65/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist

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References

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