CVE-2021-23017
Off-by-one Error
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.
Official description from the CVE record, published by f5. Copyright © 1999-2026 The MITRE Corporation. See /security/cve/legal for the CVE license. View the record on cve.org
Key data
EPSS
Exploit Prediction Scoring System by FIRST: an estimate of the probability that exploitation activity will be observed in the next 30 days.
- Score
- 0.53461 (53.5% probability)
- Percentile
- 99.0%
- Scores of
- Nov 10, 2026
- Model
- v2026.06.15
Weakness (CWE)
CWE catalog version 5.0.
CWE names: Copyright © 2006-2026, The MITRE Corporation. See /security/cve/legal for the CWE license.
- CWE-193Off-by-one Error
Affected products
Products listed in the CVE record, as the CNA published them.
Nginx Web Server, Nginx Plus
- affected: Nginx Web Server versions 0.6.18 thru 1.20.0 before 1.20.1, Nginx plus versions R13 thru R23 before R23 P1. Nginx plus version R24 before R24 P1
References
Links listed in the CVE record. They lead to other sites, which CubePath does not control.
- support.f5.com/csp/article/K12331123%2C
- mailman.nginx.org/pipermail/nginx-announce/2021/000300.html
- [apisix-notifications] 20210607 [GitHub] [apisix-website] Serendipity96 opened a new pull request #362: feat: add new blog (lists.apache.org)mailing-list
- [apisix-notifications] 20210608 [GitHub] [apisix-website] liuxiran commented on a change in pull request #362: docs: added "Apache APISIX not affected by NGINX CVE-2021-23017" (lists.apache.org)mailing-list
- [apisix-notifications] 20210608 [GitHub] [apisix-website] netlify[bot] edited a comment on pull request #362: docs: added "Apache APISIX not affected by NGINX CVE-2021-23017" (lists.apache.org)mailing-list
- [apisix-notifications] 20210608 [GitHub] [apisix-website] liuxiran merged pull request #362: docs: added "Apache APISIX not affected by NGINX CVE-2021-23017" (lists.apache.org)mailing-list
- [apisix-notifications] 20210608 [apisix-website] branch master updated: docs: added "Apache APISIX not affected by NGINX CVE-2021-23017" (#362) (lists.apache.org)mailing-list
- FEDORA-2021-b37cffac0d (lists.fedoraproject.org)vendor-advisory
- FEDORA-2021-393d698493 (lists.fedoraproject.org)vendor-advisory
- oracle.com/security-alerts/cpuoct2021.html
- security.netapp.com/advisory/ntap-20210708-0006
- oracle.com/security-alerts/cpujan2022.html
- oracle.com/security-alerts/cpuapr2022.html
- packetstormsecurity.com/files/167720/Nginx-1.20.0-Denial-Of…
Timeline
- ID reserved
- Record published
- Record last updated
Look up another CVE
About CubePath
CubePath is a cloud provider with data centers in Europe and the United States. It offers VPS, bare metal servers and DDoS protection.
Data from the CVE Program (MITRE), CISA KEV and FIRST EPSS. CVSS is owned by FIRST and used by permission. Not affiliated with or endorsed by MITRE, CISA or FIRST. Data as of Nov 10, 2026, 19:51 UTC. Sources and licenses