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CVE-2026-40303— zrok allows unauthenticated DoS via unbounded memory allocation in striped session cookie parsing

Quick assessment

Affected
openziti zrok
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

zrok是OpenZiti开源的一个安全的互联网共享工具。 zrok 2.0.1之前版本存在安全漏洞，该漏洞源于对cookie块数量缺少上限检查，可能导致拒绝服务攻击。

CVSS 7.5 · High EPSS 0.59% · P47

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking
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I. Basic Information for CVE-2026-40303

Vulnerability Information
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Vulnerability Title
zrok allows unauthenticated DoS via unbounded memory allocation in striped session cookie parsing
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
未加控制的资源消耗(资源穷尽)
Source: CVE Program / CVE List V5
Vulnerability Title
zrok 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
zrok是OpenZiti开源的一个安全的互联网共享工具。 zrok 2.0.1之前版本存在安全漏洞，该漏洞源于对cookie块数量缺少上限检查，可能导致拒绝服务攻击。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
openziti zrok < 2.0.1 -

II. Public POCs for CVE-2026-40303

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III. Intelligence Information for CVE-2026-40303

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Vendor Advisories for CVE-2026-40303 (1)

Same Patch Batch · openziti · 2026-04-17 · 3 CVEs total

CVE-2026-40302 6.1 MEDIUM zrok has reflected XSS in GitHub OAuth callback via unsanitized refreshInterval error rend
CVE-2026-40304 5.3 MEDIUM zrok's broken ownership check in DELETE /api/v2/unaccess allows non-admin to delete global

IV. Related Vulnerabilities

Same product: zrok
Same vendor: openziti
Same weakness: CWE-400

V. Comments for CVE-2026-40303

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