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Vulnerability record · CVE-2019-9900 · published 25 April 2019

CVE-2019-9900: Envoyproxy envoy injection vulnerability

Envoyproxy · Envoy

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.

8.3 CVSS 3.1 High EPSS 3.7% · top 10.6% CWE-74 · Injection
8.3CVSS 3.1 base score, v2 7.5
3.7%EPSS exploitation probability, 30 days
NoNot in CISA KEV
2Affected product versions listed by NVD
10References, 4 tagged exploit
17 Jun 2026Last modified by NVD

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.

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

Affected products

2 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://access.redhat.com/errata/RHSA-2019:0741 Third Party Advisory
https://github.com/envoyproxy/envoy/issues/6434 ExploitIssue TrackingThird Party Advisory
https://github.com/envoyproxy/envoy/security/advisories/GHSA-x74r-f4mw-c32h ExploitMitigationThird Party Advisory
https://groups.google.com/forum/#%21topic/envoy-announce/VoHfnDqZiAM
https://www.envoyproxy.io/docs/envoy/v1.9.1/intro/version_history Release NotesVendor Advisory
https://access.redhat.com/errata/RHSA-2019:0741 Third Party Advisory
https://github.com/envoyproxy/envoy/issues/6434 ExploitIssue TrackingThird Party Advisory
https://github.com/envoyproxy/envoy/security/advisories/GHSA-x74r-f4mw-c32h ExploitMitigationThird Party Advisory
https://groups.google.com/forum/#%21topic/envoy-announce/VoHfnDqZiAM
https://www.envoyproxy.io/docs/envoy/v1.9.1/intro/version_history Release NotesVendor Advisory

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Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2019-9900), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.