CVE-2021-23017

CVE-2021-23017 is a high-severity vulnerability in F5 Nginx with a CVSS 3.x base score of 7.7. Its EPSS exploit-prediction score of 53% places it in the 99th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-193.

Key facts

Description

A security issue in nginx resolver was identified, which might allow an attacker who is able to forge UDP packets from the DNS server to cause 1-byte memory overwrite, resulting in worker process crash or potential other impact.

Frequently asked questions

What is CVE-2021-23017?
A security issue in nginx resolver was identified, which might allow an attacker who is able to forge UDP packets from the DNS server to cause 1-byte memory overwrite, resulting in worker process crash or potential other impact.
How severe is CVE-2021-23017?
CVE-2021-23017 has a CVSS 3.x base score of 7.7, rated high severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability low.
Is CVE-2021-23017 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 53% (99th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-23017?
CVE-2021-23017 primarily affects F5 Nginx. In total, 25 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-23017?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-23017 published?
CVE-2021-23017 was published on 2021-06-01 and last updated on 2026-06-17.

References

Affected products (25)

More vulnerabilities in F5 Nginx

All CVEs affecting F5 Nginx →

Other CWE-193 (Off-by-one Error) vulnerabilities

Browse all CWE-193 (Off-by-one Error) vulnerabilities →

Threat intelligence

Threat-intel indicators referencing this CVE: