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

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