{"id":"CVE-2021-23017","published":"2021-06-01T12:28:09Z","modified":"2024-08-03T18:58:26Z","title":"A security issue in nginx resolver was identified, which might allow an attacker who is able to forge UDP packets from…","vendor":null,"product":null,"tier":"core","eol":null,"affectedVersions":[{"vendor":"n/a","product":"Nginx Web Server, Nginx Plus","versions":["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"]}],"description":{"text":"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.","provenance":"source","from":"CVE.org"},"summary":{"text":"The flaw is an off-by-one error in the nginx resolver component, which handles DNS responses. An attacker who can forge UDP packets appearing to come from the DNS server can trigger a one-byte memory overwrite, crashing a worker process and potentially enabling other impact.","provenance":"ai","model":"claude-haiku-5-5","generatedAt":"2026-10-23T07:15:50Z"},"cvss":null,"epss":{"score":0.53461,"percentile":0.98991,"date":"2026-10-31","provenance":"source"},"kev":null,"vulncheckKev":null,"exploited":false,"otx":null,"cwes":[{"id":"CWE-193","name":"Off-by-one Error"}],"references":[{"url":"https://support.f5.com/csp/article/K12331123%2C","tags":["x_refsource_MISC"]},{"url":"http://mailman.nginx.org/pipermail/nginx-announce/2021/000300.html","tags":["x_refsource_MISC"]},{"url":"https://lists.apache.org/thread.html/r6fc5c57b38e93e36213e9a18c8a4e5dbd5ced1c7e57f08a1735975ba%40%3Cnotifications.apisix.apache.org%3E","tags":["mailing-list","x_refsource_MLIST"]},{"url":"https://lists.apache.org/thread.html/r37e6b2165f7c910d8e15fd54f4697857619ad2625f56583802004009%40%3Cnotifications.apisix.apache.org%3E","tags":["mailing-list","x_refsource_MLIST"]},{"url":"https://lists.apache.org/thread.html/rf318aeeb4d7a3a312734780b47de83cefb7e6995da0b2cae5c28675c%40%3Cnotifications.apisix.apache.org%3E","tags":["mailing-list","x_refsource_MLIST"]},{"url":"https://lists.apache.org/thread.html/r4d4966221ca399ce948ef34884652265729d7d9ef8179c78d7f17e7f%40%3Cnotifications.apisix.apache.org%3E","tags":["mailing-list","x_refsource_MLIST"]},{"url":"https://lists.apache.org/thread.html/rf232eecd47fdc44520192810560303073cefd684b321f85e311bad31%40%3Cnotifications.apisix.apache.org%3E","tags":["mailing-list","x_refsource_MLIST"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/GNKOP2JR5L7KCIZTJRZDCUPJTUONMC5I/","tags":["vendor-advisory","x_refsource_FEDORA"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/7SFVYHC7OXTEO4SMBWXDVK6E5IMEYMEE/","tags":["vendor-advisory","x_refsource_FEDORA"]},{"url":"https://www.oracle.com/security-alerts/cpuoct2021.html","tags":["x_refsource_MISC"]},{"url":"https://security.netapp.com/advisory/ntap-20210708-0006/","tags":["x_refsource_CONFIRM"]},{"url":"https://www.oracle.com/security-alerts/cpujan2022.html","tags":["x_refsource_MISC"]},{"url":"https://www.oracle.com/security-alerts/cpuapr2022.html","tags":["x_refsource_MISC"]},{"url":"http://packetstormsecurity.com/files/167720/Nginx-1.20.0-Denial-Of-Service.html","tags":["x_refsource_MISC"]}],"techniques":[],"reports":[{"id":"SRC-b804e28bf5894dd4955f","title":"Whitepaper Name Goes","publisher":"trustwave.com","url":"https://www.trustwave.com/hubfs/Web/Library/Documents_pdf/Trustwave_SpiderLabs_2023_Hospitality_Sector_Threat_Landscape.pdf","date":null,"mentions":[{"quote":"▪ Apache Tomcat HTTP Request Smuggling (CVE-2021-23017)","start":45542,"end":45597}]}],"affected":[],"advisories":[],"euvd":{"id":"EUVD-2021-10135","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2021-10135","exploited":false,"exploitedSince":null,"provenance":"source"},"exploits":[{"id":50973,"url":"https://www.exploit-db.com/exploits/50973","title":"Nginx 1.20.0 - Denial of Service (DOS)","type":"remote","platform":"multiple","date":"2022-07-11","verified":false,"provenance":"source"}],"exploitSources":{"exploitdb":{"count":1,"earliest":"2022-07-11"},"pocGithub":{"count":7,"skipped":2,"earliest":"2021-12-17","earliestUrl":"https://github.com/niandy/nginx-patch","repos":[{"name":"M507/CVE-2021-23017-PoC","url":"https://github.com/M507/CVE-2021-23017-PoC","stars":136,"created":"2022-06-30"},{"name":"niandy/nginx-patch","url":"https://github.com/niandy/nginx-patch","stars":1,"created":"2021-12-17"},{"name":"lakshit1212/CVE-2021-23017-PoC","url":"https://github.com/lakshit1212/CVE-2021-23017-PoC","stars":1,"created":"2023-07-20"},{"name":"z3usx01/CVE-2021-23017-POC","url":"https://github.com/z3usx01/CVE-2021-23017-POC","stars":1,"created":"2024-12-08"},{"name":"6lj/EVIL-CVE-2021-23017-Update-2025","url":"https://github.com/6lj/EVIL-CVE-2021-23017-Update-2025","stars":1,"created":"2025-09-04"}]},"first":{"date":"2021-12-17","source":"PoC-in-GitHub","url":"https://github.com/niandy/nginx-patch"},"provenance":"source"},"exploitRefs":["http://packetstormsecurity.com/files/167720/Nginx-1.20.0-Denial-Of-Service.html"],"flow":[],"timeline":[{"date":"2021-06-01","kind":"published","label":"Published (CVE.org)","url":"https://www.cve.org/CVERecord?id=CVE-2021-23017","provenance":"source"},{"date":"2021-12-17","kind":"exploit-public","label":"First public exploit: PoC-in-GitHub; later: Exploit-DB 2022-07-11","url":"https://github.com/niandy/nginx-patch","provenance":"source"}],"speed":{"daysToPublicExploit":199,"firstExploitFrom":"PoC-in-GitHub","daysToKev":null},"priority":{"score":28.7,"factors":[{"name":"In a KEV catalog","points":0.0,"detail":"not listed"},{"name":"Recent KEV listing","points":0.0,"detail":"not listed"},{"name":"Known ransomware use","points":0.0,"detail":"not known"},{"name":"EPSS percentile","points":19.8,"detail":"percentile 0.9899"},{"name":"Named in threat reports","points":3.87,"detail":"1 report"},{"name":"Public exploit code","points":5.0,"detail":"1 Exploit-DB entry; 1 NVD exploit link; 7 PoC-in-GitHub repos"},{"name":"Mentioned in OTX pulses","points":0.0,"detail":"0 pulses"},{"name":"CVSS severity","points":0.0,"detail":"no CVSS"},{"name":"End-of-life product","points":0.0,"detail":"supported or unknown"}]}}