Input validation error in envoy - CVE-2019-9900
Published: November 8, 2019 / Updated: June 24, 2026
Vulnerability identifier: #VU135104
CSH Severity: High
CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N]
CVE-ID: CVE-2019-9900
CWE-ID: CWE-20
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to bypass access controls and gain access to unauthorized resources.
The vulnerability exists due to improper input validation in HTTP/1.x header parsing and header matching logic when processing HTTP/1.x requests with header values containing embedded NUL characters. A remote attacker can send a specially crafted HTTP request with embedded NUL characters in header values to bypass access controls and gain access to unauthorized resources.
The issue affects HTTP/1.x traffic and exploitation depends on configurations that use header-based access control, authorization, routing, or rate limiting decisions.
Affected software
envoy
How to mitigate CVE-2019-9900
Install security update from vendor's website.
envoy - update to 1.9.1