What’s Vulnerable › Vulnerabilities

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

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-04-17 · updated 2026-10-26
• Weakness: CWE-400

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.

Affected products

• openziti zrok: before 2.0.1 — fixed in 2.0.1

How to fix

Upgrade to a fixed version: openziti zrok 2.0.1. Check the vendor advisory for mitigations.

References

• https://github.com/openziti/zrok/releases/tag/v2.0.1
• https://github.com/openziti/zrok/security/advisories/GHSA-cpf9-ph2j-ccr9

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