{"id":"CVE-2019-15226","url":"https://www.cyber-defence.io/tools/cve/CVE-2019-15226","generatedAt":"2026-10-28T21:32:19.892Z","title":"A remote attacker may craft a request that stays below the maximum request header size but consists of many thousands of small headers to consume CPU and result in a denial-of-service attack.","description":"Upon receiving each incoming request header data, Envoy will iterate over existing request headers to verify that the total size of the headers stays below a maximum limit. The implementation in versions 1.10.0 through 1.11.1 for HTTP/1.x traffic and all versions of Envoy for HTTP/2 traffic had O(n^2) performance characteristics. A remote attacker may craft a request that stays below the maximum request header size but consists of many thousands of small headers to consume CPU and result in a denial-of-service attack.","published":"2019-10-09T16:15:15.000Z","lastModified":"2026-06-17T02:19:53.000Z","status":"Modified","sourceIdentifier":"cve@mitre.org","cvss":{"version":"3.1","score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},"cwe":["CWE-400"],"affected":["envoyproxy/envoy"],"epss":{"score":0.64517,"percentile":0.99234,"date":"2026-10-27","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"urgent","text":"EPSS puts the probability of exploitation in the next 30 days at 64.5%, higher than 99% of all known CVEs. Patch or mitigate before the next change window."},"changes":[],"references":[{"url":"https://github.com/envoyproxy/envoy/commit/afc39bea36fd436e54262f150c009e8d72db5014","tags":["Patch","Third Party Advisory"],"source":"cve@mitre.org"},{"url":"https://github.com/envoyproxy/envoy/commits/master","tags":["Third Party Advisory"],"source":"cve@mitre.org"},{"url":"https://github.com/envoyproxy/envoy/issues/8520","tags":["Third Party Advisory"],"source":"cve@mitre.org"},{"url":"https://github.com/envoyproxy/envoy/commit/afc39bea36fd436e54262f150c009e8d72db5014","tags":["Patch","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://github.com/envoyproxy/envoy/commits/master","tags":["Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://github.com/envoyproxy/envoy/issues/8520","tags":["Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2019-15226","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}