CVE-2019-9900

Name: CVE-2019-9900
Creator: NVD / NIST
Published: 2019-04-25T15:29:01.497+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 8.3/10EPSS 3.73%

Last modified Jun 17, 2026

CVE-2019-9900 is a high-severity vulnerability rated 8.3/10 on the CVSS scale. 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.. EPSS estimates a 3.73% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

8.3/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L

EPSS Probability

3.73%

88.4th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-74

Affected Software

Vendor	Product	Versions
Envoyproxy	Envoy	<= 1.9.0
Redhat	Openshift Service Mesh	All versions

References

https://access.redhat.com/errata/RHSA-2019:0741Third Party Advisory
https://github.com/envoyproxy/envoy/issues/6434Exploit, Issue Tracking, Third Party Advisory
https://github.com/envoyproxy/envoy/security/advisories/GHSA-x74r-f4mw-c32hExploit, Mitigation, Third Party Advisory
https://groups.google.com/forum/#%21topic/envoy-announce/VoHfnDqZiAM
https://www.envoyproxy.io/docs/envoy/v1.9.1/intro/version_historyRelease Notes, Vendor Advisory
https://access.redhat.com/errata/RHSA-2019:0741Third Party Advisory
https://github.com/envoyproxy/envoy/issues/6434Exploit, Issue Tracking, Third Party Advisory
https://github.com/envoyproxy/envoy/security/advisories/GHSA-x74r-f4mw-c32hExploit, Mitigation, Third Party Advisory
https://groups.google.com/forum/#%21topic/envoy-announce/VoHfnDqZiAM
https://www.envoyproxy.io/docs/envoy/v1.9.1/intro/version_historyRelease Notes, Vendor Advisory

Timeline

Published: Apr 25, 2019
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2019-9900?

How severe is CVE-2019-9900?

CVE-2019-9900 has a CVSS score of 8.3/10 (HIGH severity). The EPSS model estimates a 3.73% probability of exploitation in the next 30 days.

How do I fix CVE-2019-9900?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2019-9900?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST