CVE-2019-9900

When parsing HTTP/1.x header values, Envoy 1.9.0 and before does not reject embedded zero...

6.5 MediumFix available

CVE-2019-9900 is a medium vulnerability (CVSS 6.5) in Envoyproxy Envoy, published April 25, 2019. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 3.73%, the 89th percentile. Fixed in servicemesh-proxy 0:0.9.1-1.el7.

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.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: High
Privileges needed: None
User interaction: None

What an attacker can affect

Confidentiality: Low
Integrity: Low
Availability: Low

Exploit likelihood

3.73%Up 2.2 points since Apr 14, 2021

What each source reports

CVE List Score used 6.5

Record: CVE-2019-9900
CVSS 3.0: 6.5 MediumCVSS:3.0/AC:H/AV:N/A:L/C:L/I:L/PR:N/S:C/UI:N
Updated: 2026-11-02

EUVDEUVD-2019-19256 6.5

Record: EUVD-2019-19256
CVSS 3.0: 6.5 MediumCVSS:3.0/AC:H/AV:N/A:L/C:L/I:L/PR:N/S:C/UI:N
Updated: 2026-11-03

GitHub AdvisoriesGHSA-h9r7-c397-3wqr 8.3

When parsing HTTP/1.x header values, Envoy 1.9.0 and before does not reject embedded zero...

Record: GHSA-h9r7-c397-3wqr
CVSS 3.1: 8.3 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L
Weakness: CWE-20, CWE-74
Updated: 2026-11-02

NVD 8.3

Record: CVE-2019-9900
CVSS 3.1: 8.3 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L
CVSS 3.0: 6.5 MediumCVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:L
CVSS 2.0: 7.5 HighAV:N/AC:L/Au:N/C:P/I:P/A:P
Weakness: CWE-74
Updated: 2026-11-02

OSV 8.3

Record: CVE-2019-9900
CVSS 3.1: 8.3 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L
Updated: 2026-11-02

OSVRHSA-2019:0741 8.3

Red Hat Security Advisory: Istio-Proxy Security Update

Record: RHSA-2019:0741
CVSS 3.0: 8.3 HighCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L
Updated: 2026-11-02

Affected products

Affected packages

Affected packages
Package	Affected	Fixed
`servicemesh-proxy` Red Hat:service_mesh:0	before 0:0.9.1-1.el7	0:0.9.1-1.el7

History

History
When	Changed	Sources
2026-11-03	aliases	EUVD
2026-11-02	created	CVE List, GitHub Advisories, NVD, OSV

References

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