CVE-2021-23017

HIGHNVD 7.79.4▲

7.7

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.

CVSS v3: 7.7
EG Score: 9.4(medium)
EPSS: 98.8%
KEV: Not listed

Published

June 1, 2021

Last Modified

November 21, 2024

References (28)

Patch Availability(10)

Vendor / Ecosystem	Fixed in / Patch	Released	Source
redhat	nginx:1.20-8050020211221125012.c5368500	2022-01-31	redhat
redhat	rhacm2/management-ingress-rhel7:v2.3.3-3	2021-10-20	redhat
redhat	3scale-amp2/zync-rhel8:1.14.0-3	2021-10-14	redhat
redhat	rhacm2/acm-must-gather-rhel8:v2.1.11-2	2021-09-23	redhat
redhat	ansible-tower-38/ansible-tower-rhel7:3.8.4-1	2021-09-08	redhat
redhat	python-pulpcore-0:3.7.6-1.el8pc	2021-07-29	redhat
redhat	nginx:1.16-8020020210526102648.4cda2c84	2021-06-08	redhat
redhat	nginx:1.18-8040020210526100943.522a0ee4	2021-06-07	redhat
redhat	rh-nginx116-nginx-1:1.16.1-6.el7	2021-06-07	redhat
redhat	rh-nginx118-nginx-1:1.18.0-3.el7	2021-06-07	redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

CWE-193Off-by-one Error

All Vendor Advisories

(11)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 7× in last 7d / 7× in last 30d)

Every time one of our enrichment pipelines (NVD, MITRE cvelistV5, EPSS, CISA KEV, GHSA, OSV, vendor advisories) ran against this CVE. Most recent first.

2026-05-26 15:49 UTCEG score recompute
2026-05-26 15:49 UTCVendor advisory
2026-05-26 15:49 UTCGHSA enrichment
2026-05-26 13:42 UTCepss_batch
2026-05-26 13:42 UTCepss_batch
2026-05-26 07:17 UTCepss_batch
2026-05-26 07:17 UTCepss_batch

Frequently asked(5)

What is CVE-2021-23017?

CVE-2021-23017 is a high vulnerability published on June 1, 2021. 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.

When was CVE-2021-23017 disclosed?

CVE-2021-23017 was first published in the National Vulnerability Database on June 1, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.

Is CVE-2021-23017 actively exploited?

CVE-2021-23017 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 98.8% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2021-23017?

CVE-2021-23017 has a CVSS v3 base score of 7.7 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 9.4.

How do I remediate CVE-2021-23017?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-23017, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2021-23017

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Is Your Infrastructure Affected by CVE-2021-23017?

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CVE-2021-23017

Published

Last Modified

References (28)

Patch Availability(10)

Weakness Classification(1)

All Vendor Advisories

Data Freshness Timeline

Frequently asked(5)

Dependency Blast Radius

Is Your Infrastructure Affected by CVE-2021-23017?

Same vendor

Same CWE

CVE-2021-23017

📅 Published

🔄 Last Modified

🔗 References (28)

Patch Availability(10)

Weakness Classification(1)

All Vendor Advisories

Data Freshness Timeline

❓ Frequently asked(5)

Dependency Blast Radius

Is Your Infrastructure Affected by CVE-2021-23017?

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References (28)

Frequently asked(5)

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