{"id":"CVE-2019-9900","url":"https://www.cyber-defence.io/tools/cve/CVE-2019-9900","generatedAt":"2026-10-27T21:16:18.872Z","title":"This allows remote attackers crafting header values containing embedded NUL characters to potentially bypass header matching rules, gaining access to unauthorized resources.","description":"When parsing HTTP/1.x header values, Envoy 1.9.0 and before does not reject embedded zero characters (NUL, ASCII 0x0). This allows remote attackers crafting header values containing embedded NUL characters to potentially bypass header matching rules, gaining access to unauthorized resources.","published":"2019-04-25T15:29:01.000Z","lastModified":"2026-06-17T02:44:49.000Z","status":"Modified","sourceIdentifier":"cve@mitre.org","cvss":{"version":"3.1","score":8.3,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L"},"cwe":["CWE-74"],"affected":["envoyproxy/envoy","redhat/openshift service mesh"],"epss":{"score":0.03732,"percentile":0.89751,"date":"2026-10-26","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (3.73%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[],"references":[{"url":"https://access.redhat.com/errata/RHSA-2019:0741","tags":["Third Party Advisory"],"source":"cve@mitre.org"},{"url":"https://github.com/envoyproxy/envoy/issues/6434","tags":["Exploit","Issue Tracking","Third Party Advisory"],"source":"cve@mitre.org"},{"url":"https://github.com/envoyproxy/envoy/security/advisories/GHSA-x74r-f4mw-c32h","tags":["Exploit","Mitigation","Third Party Advisory"],"source":"cve@mitre.org"},{"url":"https://groups.google.com/forum/#%21topic/envoy-announce/VoHfnDqZiAM","source":"cve@mitre.org"},{"url":"https://www.envoyproxy.io/docs/envoy/v1.9.1/intro/version_history","tags":["Release Notes","Vendor Advisory"],"source":"cve@mitre.org"},{"url":"https://access.redhat.com/errata/RHSA-2019:0741","tags":["Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://github.com/envoyproxy/envoy/issues/6434","tags":["Exploit","Issue Tracking","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://github.com/envoyproxy/envoy/security/advisories/GHSA-x74r-f4mw-c32h","tags":["Exploit","Mitigation","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://groups.google.com/forum/#%21topic/envoy-announce/VoHfnDqZiAM","source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://www.envoyproxy.io/docs/envoy/v1.9.1/intro/version_history","tags":["Release Notes","Vendor Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2019-9900","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."}