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No exploitation reportedFix available

CVE-2019-9900

No exploitation reported by the sources we read.

  • Published2019-04-25
  • WeaknessCWE-74

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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.

Timeline

dates in UTC
  1. 2019-04-2515:29CVE publishedNVD

Versions per branch

NVD
Envoy
BranchAffectedFixed in
1.9≤ 1.9.0no fix published
Redhat openshift service mesh
BranchAffectedFixed in
—all versionsno fix published

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • servicemesh-proxyRed Hat:service_mesh:0all versions · fixed in 0:0.9.1-1.el7

Vendor advisories

  • CVE-2019-9900 Red Hat Product Security2 products fixed

    istio/envoy: Authorization bypass via null characters injection in HTTP/1.x

  • RHSA-2019:0741 Red Hat Product Security2 products fixed

    Red Hat Security Advisory: Istio-Proxy Security Update

Full record on NVD

Fix

  1. Vendor fix Red Hat Product Security RHSA-2019:0741 · 2 productsBefore applying this update, make sure all previously released errata relevant to your system have been applied. For details on how to apply this update, refer to: https://access.redhat.com/articles/11258

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof of concept
Metasploit modules
none listed
Metasploit Framework

Sources

  • NVDCVSS 3.18.3read 2026-10-23
  • CNACVSS 3.06.5known since 2026-10-23
  • NVDCVSS 2.07.5read 2026-10-23
  • NVDweakness (CWE)CWE-74read 2026-10-23
  • FIRST EPSSEPSS score3.7 %2026-11-08
  • OSVaffected packages—
  • GitHub Advisoriesadvisory—

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L
Published
2019-04-25
Last Modified
2026-06-17
NVD status
Modified
GitHub Advisory
GHSA-h9r7-c397-3wqr

Frequently asked questions

What is CVE-2019-9900?

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.

Is CVE-2019-9900 actively exploited?

Active exploitation of CVE-2019-9900 has not been confirmed. Its EPSS score was 3.7% on 2026-11-08, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2019-9900?

CVE-2019-9900 has a CVSS v3 base score of 8.3 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L.

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