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CVE-2019-9900· NVD / CVE Program· CNA mitre

When parsing HTTP/1.x header values, Envoy 1.9.0 and before does not reject embedded zero characters (NUL, ASCII 0x0).

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.

HighCVSS 8.3 · v3.1—No exploit Fix available
Published
Apr 25, 2019
Updated
Jun 16, 2026
EPSS
3.7% · 89th percentile
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Report tools

JSON

Action score

34

Monitor

Low priority for now.

CVSS
33 / 40 · 8.3 / 10
CISA KEV
0 / 30 · Not listed
EPSS
1 / 30 · 3.7%

CNA vs NVD score

NVD
8.3
CNA · mitre
6.5
1.8 point gap

CVSS:3.0/AC:H/AV:N/A:L/C:L/I:L/PR:N/S:C/UI:N

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Noroxi analysis

No Noroxi analysis for this record yet

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Affected systems

VendorProduct
envoyproxyenvoy
redhatopenshift service mesh

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • envoyproxy envoyup to 1.9.0 inclusive
  • redhat openshift service meshall versions

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Red Hat:service_mesh:0servicemesh-proxybefore 0:0.9.1-1.el70:0.9.1-1.el7

Same product

envoyproxy: all records

Other highest-scoring records for the same primary product.

  • CVE-2024-30255HTTP/2: CPU exhaustion due to CONTINUATION frame flood
    56Plan
  • CVE-2024-27919HTTP/2: memory exhaustion due to CONTINUATION frame flood
    56Plan
  • CVE-2021-29492Bypass of path matching rules using escaped slash characters
    53Plan
  • CVE-2019-15226Upon receiving each incoming request header data, Envoy will iterate over existing request headers to verify that the total size of the head
    49Plan
  • CVE-2019-9901Envoy 1.9.0 and before does not normalize HTTP URL paths.
    41Plan
  • CVE-2019-18802An issue was discovered in Envoy 1.12.0.
    40Plan

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
red hat:servicemesh-proxy0:0.9.1-1.el7 · Red Hat:service_mesh:0Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
low · data can be read
Integrity
low · data or configuration can be modified
Availability
low · the service can be disrupted

Impact can extend beyond the vulnerable component (scope changes).

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Changed
Confidentiality impact
Low
Integrity impact
Low
Availability impact
Low

Weakness class (CWE)

CWE-74 · Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Change log

  1. Fix✗ → ✓

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References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records