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No exploitation reportedFix available

CVE-2021-20322

No exploitation reported by the sources we read.

  • Published2022-02-18
  • Fixed in5.13.14 · 5.10.62 · 5.4.157 · 4.19.215
  • WeaknessCWE-330

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

A flaw in the processing of received ICMP errors (ICMP fragment needed and ICMP redirect) in the Linux kernel functionality was found to allow the ability to quickly scan open UDP ports. This flaw allows an off-path remote user to effectively bypass the source port UDP randomization. The highest threat from this vulnerability is to confidentiality and possibly integrity, because software that relies on UDP source port randomization are indirectly affected as well.

Timeline

dates in UTC
  1. 2022-02-1818:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 18:48 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-20322?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-20322?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Linux linux kernel
BranchAffectedFixed in
5.x≥ 5.11, < 5.13.145.13.14
5.x≥ 5.5, < 5.10.625.10.62
5.4≥ 4.20, < 5.4.1575.4.157
4.x≥ 4.15, < 4.19.2154.19.215
Debian debian linux
BranchAffectedFixed in
9.0= 9.0no fix published
10.0= 10.0no fix published
Fedoraproject fedora
BranchAffectedFixed in
34.x= 34no fix published

18 more products in the sources.

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

  1. Update Linux linux kernel to 5.13.14 · 5.10.62 · 5.4.157 · 4.19.215

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub

Sources

  • NVDCVSS 3.17.4read 2026-10-23
  • NVDCVSS 2.05.8read 2026-10-23
  • CNAweakness (CWE)CWE-330read 2026-10-23
  • NVDweakness (CWE)CWE-330read 2026-10-23
  • FIRST EPSSEPSS score6.9 %2026-10-22

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Published
2022-02-18
Last Modified
2026-07-30
NVD status
Analyzed

Frequently asked questions

What is CVE-2021-20322?

A flaw in the processing of received ICMP errors (ICMP fragment needed and ICMP redirect) in the Linux kernel functionality was found to allow the ability to quickly scan open UDP ports. This flaw allows an off-path remote user to effectively bypass the source port UDP randomization. The highest threat from this vulnerability is to confidentiality and possibly integrity, because software that relies on UDP source port randomization are indirectly affected as well.

Is CVE-2021-20322 actively exploited?

Active exploitation of CVE-2021-20322 has not been confirmed. Its EPSS score was 6.9% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-20322?

CVE-2021-20322 has a CVSS v3 base score of 7.4 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N.

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