CVE-2019-18802
CVSS v3
9.8
CRITICAL
EPSS Score
2.5 %
exploit probability, as of 2026-09-25
CISA KEV
No
known exploited
Exploitation
—
SSVC status
Description
An issue was discovered in Envoy 1.12.0. An untrusted remote client may send an HTTP header (such as Host) with whitespace after the header content. Envoy will treat "header-value " as a different string from "header-value" so for example with the Host header "example.com " one could bypass "example.com" matchers.
Technical details
- Published
- 2019-12-13
Frequently asked questions
What is CVE-2019-18802?
An issue was discovered in Envoy 1.12.0. An untrusted remote client may send an HTTP header (such as Host) with whitespace after the header content. Envoy will treat "header-value " as a different string from "header-value" so for example with the Host header "example.com " one could bypass "example.com" matchers.
Is CVE-2019-18802 actively exploited?
Active exploitation of CVE-2019-18802 has not been confirmed. Its EPSS score was 2.5% on 2026-09-25, the estimated probability of exploitation in the next 30 days.
What is the CVSS score for CVE-2019-18802?
CVE-2019-18802 has a CVSS v3 base score of 9.8 (CRITICAL severity).
Is CVE-2019-18802 affecting your environment?
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