CVE-2026-40303Network attack vector

Unauthenticated proxy termination via unbounded cookie allocation

Published Apr 17, 2026 · Updated Apr 17, 2026

Resource exhaustion in OpenZiti zrok before 2.0.1 allows remote attackers to terminate OAuth-protected proxy processes via crafted cookies. GetSessionCookie converts an attacker-controlled cookie stripe count directly into the length of a string slice, without bounding it before JWT validation. A single unauthenticated HTTP request can allocate gigabytes; sustained requests can terminate the affected publicProxy or dynamicProxy process and interrupt every share it serves.

CVSS severity7.5
High
EPSS probability0.45%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Resource exhaustion in OpenZiti zrok before 2.0.1 allows remote attackers to terminate OAuth-protected proxy processes via crafted cookies. GetSessionCookie converts an attacker-controlled cookie stripe count directly into the length of a string slice, without bounding it before JWT validation. A single unauthenticated HTTP request can allocate gigabytes; sustained requests can terminate the affected publicProxy or dynamicProxy process and interrupt every share it serves.

The record

CVE
CVE-2026-40303
Published
Apr 17, 2026
Updated
Apr 17, 2026
Vendor
OpenZiti
Product
zrok
Classifications
CWE-789, CWE-400, T1499.003
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 17, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 17, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 2.0.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

OpenZiti · zrokversion=< 2.0.1

Published CVSS scores

7.5GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-789Memory Allocation with Excessive Size Value
CWE-400Uncontrolled Resource Consumption
T1499.003Application Exhaustion Flood

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo