CVE-2019-9900
This allows remote attackers crafting header values containing embedded NUL characters to potentially bypass header matching rules, gaining access to unauthorized resources.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (3.73%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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
- 8.3 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L
- EPSS
- 3.73% probability · 90th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-74
- Affected
- envoyproxy/envoy · redhat/openshift service mesh
- Source
- cve@mitre.org
EPSS 3.7% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
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
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.