CVE-2019-9900
CVSS v3
8.3
HIGH
EPSS Score
3.7 %
exploit probability, as of 2026-09-25
CISA KEV
No
known exploited
Exploitation
—
SSVC status
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.
Technical details
- Published
- 2019-04-25
Frequently asked questions
What is CVE-2019-9900?
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.
Is CVE-2019-9900 actively exploited?
Active exploitation of CVE-2019-9900 has not been confirmed. Its EPSS score was 3.7% on 2026-09-25, the estimated probability of exploitation in the next 30 days.
What is the CVSS score for CVE-2019-9900?
CVE-2019-9900 has a CVSS v3 base score of 8.3 (HIGH severity).
Is CVE-2019-9900 affecting your environment?
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