CVE-2021-20322
HIGHEPSS 94th pctlDescription
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.
How to fix
This Ubuntu release reached end-of-life on 2023-05-31. Extended security maintenance is available until 2028-04-01.
This Ubuntu release reached end-of-life on 2023-05-31. Extended security maintenance is available until 2028-04-01.
This Ubuntu release reached end-of-life on 2023-05-31. Extended security maintenance is available until 2028-04-01.
This Ubuntu release reached end-of-life on 2023-05-31. Extended security maintenance is available until 2028-04-01.
This Ubuntu release reached end-of-life on 2023-05-31. Extended security maintenance is available until 2028-04-01.
This Ubuntu release reached end-of-life on 2023-05-31. Extended security maintenance is available until 2028-04-01.
This Ubuntu release reached end-of-life on 2023-05-31. Extended security maintenance is available until 2028-04-01.
This Ubuntu release reached end-of-life on 2023-05-31. Extended security maintenance is available until 2028-04-01.
This Ubuntu release reached end-of-life on 2023-05-31. Extended security maintenance is available until 2028-04-01.
This Ubuntu release reached end-of-life on 2023-05-31. Extended security maintenance is available until 2028-04-01.
This Ubuntu release reached end-of-life on 2023-05-31. Extended security maintenance is available until 2028-04-01.
This Ubuntu release reached end-of-life on 2023-05-31. Extended security maintenance is available until 2028-04-01.
This Ubuntu release reached end-of-life on 2023-05-31. Extended security maintenance is available until 2028-04-01.
This Ubuntu release reached end-of-life on 2023-05-31. Extended security maintenance is available until 2028-04-01.
This Ubuntu release reached end-of-life on 2023-05-31. Extended security maintenance is available until 2028-04-01.
This Ubuntu release reached end-of-life on 2023-05-31. Extended security maintenance is available until 2028-04-01.
This Ubuntu release reached end-of-life on 2023-05-31. Extended security maintenance is available until 2028-04-01.
This Ubuntu release reached end-of-life on 2023-05-31. Extended security maintenance is available until 2028-04-01.
This Ubuntu release reached end-of-life on 2023-05-31. Extended security maintenance is available until 2028-04-01.
This vulnerability affects an unusually large number of packages. The highest-confidence fixes are shown above; the full list is longer. Check the referenced advisories for complete coverage.
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Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Exploit Intelligence
High risk: more likely to be exploited than 94% of all known CVEs.
References
Related Vulnerabilities
Other CWE-330 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2019-5420 | Critical | 9.8 | 92% | - | Fix |
| CVE-2021-34646 | Critical | 9.8 | 51% | - | - |
| CVE-2008-0087 | High | 7.5 | 32% | - | - |
| CVE-2017-6026 | Critical | 9.1 | 32% | - | - |
| CVE-2018-17888 | Critical | 9.8 | 30% | - | - |
| CVE-2020-11901 | Critical | 9.0 | 21% | - | Fix |
Common questions
How do I fix CVE-2021-20322?
Published advisories record a fix for 44 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.
Is CVE-2021-20322 being actively exploited?
Not that we know of. CVE-2021-20322 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 6.8% is the estimated probability that it will be exploited in the next 30 days. That is higher than 94% of all scored CVEs.
How severe is CVE-2021-20322?
CVE-2021-20322 has a CVSS v3 base score of 7.4, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2021-20322 affect?
Published advisories record a fix for linux (Debian), linux (Ubuntu), linux-aws (Ubuntu), linux-aws-hwe (Ubuntu), and 40 more. Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-07-30.