CVE-2026-40303

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.

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.

**Summary** 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. - Attack Vector: Network — exploitable via a single HTTP request with a crafted Cookie header. - Attack Complexity: Low — no preconditions or chaining required; the attacker only needs to know the cookie name (publicly derivable from any OAuth redirect). - Privileges Required: None — reached before JWT validation or any authentication check. - User Interaction: None. - Scope: Unchanged — impact is confined to the affected proxy process. - Confidentiality Impact: None. - Integrity Impact: None. Availability Impact: High — sustained or concurrent requests cause OOM process termination, taking down the proxy for all users of all shares it serves. **Affected Components** - endpoints/oauthCookies.go — GetSessionCookie (line 81) - endpoints/publicProxy/authOAuth.go — handleOAuth (line 50) — call site, pre-auth - endpoints/dynamicProxy/cookies.go — getSessionCookie (line 29) — call site

**Summary** 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. - Attack Vector: Network — exploitable via a single HTTP request with a crafted Cookie header. - Attack Complexity: Low — no preconditions or chaining required; the attacker only needs to know the cookie name (publicly derivable from any OAuth redirect). - Privileges Required: None — reached before JWT validation or any authentication check. - User Interaction: None. - Scope: Unchanged — impact is confined to the affected proxy process. - Confidentiality Impact: None. - Integrity Impact: None. Availability Impact: High — sustained or concurrent requests cause OOM process termination, taking down the proxy for all users of all shares it serves. **Affected Components** - endpoints/oauthCookies.go — GetSessionCookie (line 81) - endpoints/publicProxy/authOAuth.go — handleOAuth (line 50) — call site, pre-auth - endpoints/dynamicProxy/cookies.go — getSessionCookie (line 29) — call site