CVE-2026-40303
zrok allows unauthenticated DoS via unbounded memory allocation in striped session cookie parsing
Description
zrok is software for sharing web services, files, and network resources. Prior to version 2.0.1, endpoints.GetSessionCookie parses an attacker-supplied cookie chunk count and calls make([]string, count) with no upper bound before any token validation occurs. The function is reached on every request to an OAuth-protected proxy share, allowing an unauthenticated remote attacker to trigger gigabyte-scale heap allocations per request, leading to process-level OOM termination or repeated goroutine panics. Both publicProxy and dynamicProxy are affected. Version 2.0.1 patches the issue.
INFO
Published Date :
April 17, 2026, 9:16 p.m.
Last Modified :
April 23, 2026, 6:33 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | HIGH | [email protected] |
Solution
- Update zrok to version 2.0.1.
- Ensure all zrok instances are upgraded.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-40303.
| URL | Resource |
|---|---|
| https://github.com/openziti/zrok/releases/tag/v2.0.1 | Release Notes |
| https://github.com/openziti/zrok/security/advisories/GHSA-cpf9-ph2j-ccr9 | Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-40303 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-40303
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-40303 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-40303 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Apr. 23, 2026
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:netfoundry:zrok:*:*:*:*:*:*:*:* versions up to (excluding) 2.0.1 Added Reference Type GitHub, Inc.: https://github.com/openziti/zrok/releases/tag/v2.0.1 Types: Release Notes Added Reference Type GitHub, Inc.: https://github.com/openziti/zrok/security/advisories/GHSA-cpf9-ph2j-ccr9 Types: Vendor Advisory -
New CVE Received by [email protected]
Apr. 17, 2026
Action Type Old Value New Value Added Description zrok is software for sharing web services, files, and network resources. Prior to version 2.0.1, endpoints.GetSessionCookie parses an attacker-supplied cookie chunk count and calls make([]string, count) with no upper bound before any token validation occurs. The function is reached on every request to an OAuth-protected proxy share, allowing an unauthenticated remote attacker to trigger gigabyte-scale heap allocations per request, leading to process-level OOM termination or repeated goroutine panics. Both publicProxy and dynamicProxy are affected. Version 2.0.1 patches the issue. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Added CWE CWE-400 Added CWE CWE-789 Added Reference https://github.com/openziti/zrok/releases/tag/v2.0.1 Added Reference https://github.com/openziti/zrok/security/advisories/GHSA-cpf9-ph2j-ccr9