Concurrent Execution Using Shared Resource with Improper Synchronization ('Race Condition') (CWE-362)

Concurrent Execution Using Shared Resource with Improper Synchronization ('Race Condition')

The product contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently.

This can have security implications when the expected synchronization is in security-critical code, such as recording whether a user is authenticated or modifying important state information that should not be influenced by an outsider.

Prevalence

Medium

3 languages covered

Impact

High

4 high-severity rules

Prevention

Documented

6 fix examples

2 Prevention

How to fix this vulnerability

Prevention strategies for Race Condition based on 6 Shoulder detection rules.

🐹 Go View all Go details →

Concurrent Slice Access HIGH

Protect concurrent slice access with mutex or use channels to collect results

+10 -7 go

  func collect(items []string) []string {
-     var results []string
-     for _, item := range items {
-         go func(i string) {
-             results = append(results, process(i))
-         }(item)
-     }
-     time.Sleep(time.Second)
+     resultsCh := make(chan string, len(items))
+     for _, item := range items {
+         go func(i string) {
+             resultsCh <- process(i)
+         }(item)
+     }
+     results := make([]string, 0, len(items))
+     for i := 0; i < len(items); i++ {
+         results = append(results, <-resultsCh)
+     }
      return results
  }

Direct Map Access on Thread-Safe Struct HIGH

Use thread-safe accessor methods or sync.RWMutex for concurrent map access

+1 -1 go

  func getNodeName(node *Node) string {
-     name, ok := node.Attributes["name"].(string)
+     name, ok := node.GetAttrString("name")
      if !ok {
          return ""
      }
      return name
  }

Potential Race Condition MEDIUM

Protect shared state with sync.Mutex, atomic operations, or sync.Map

+4 -4 go

- var counter int
- func increment() {
-     go func() {
-         counter++
+ var counter int64
+ func increment() {
+     go func() {
+         atomic.AddInt64(&counter, 1)
      }()
  }

🟨 JavaScript View all JavaScript details →

Race Condition in Concurrent Operations HIGH

Use database transactions with row-level locking for atomic read-modify-write operations

+16 -3 javascript

  app.post('/withdraw', async (req, res) => {
-   const account = await Account.findOne({ where: { userId } });
-   if (account.balance >= amount) {
-     await account.update({ balance: account.balance - amount });
+   const transaction = await db.transaction();
+   try {
+     const account = await Account.findOne({
+       where: { userId },
+       lock: transaction.LOCK.UPDATE,
+       transaction
+     });
+     if (account.balance < amount) {
+       await transaction.rollback();
+       return res.status(400).json({ error: 'Insufficient funds' });
+     }
+     await account.update({ balance: account.balance - amount }, { transaction });
+     await transaction.commit();
+   } catch (e) {
+     await transaction.rollback();
+     throw e;
    }
  });

🐍 Python View all Python details →

Potential Race Condition MEDIUM

Use locks for shared data and atomic operations for file access

+6 -4 python

  import threading
  
  counter = 0
- 
- def increment():
-     global counter
-     counter += 1
+ lock = threading.Lock()
+ 
+ def increment():
+     global counter
+     with lock:
+         counter += 1
  
  threads = [threading.Thread(target=increment) for _ in range(100)]

Key Practices

Use data races, lost data, or panics
Use race conditions
Use of sync

3 Detection

Find vulnerabilities in your code

Use Shoulder to scan your codebase for Concurrent Execution Using Shared Resource with Improper Synchronization ('Race Condition') patterns. 6 rules.

terminal

# Scan with Shoulder CLI
npx @shoulderdev/cli trust --cwe=362

# Or scan entire project
npx @shoulderdev/cli trust .

Detection Rules (6)

🐹 Go 4 rules

Concurrent Slice Access HIGH

Concurrent access to slices (especially append) without synchronization can cause data races, lost data, or panics. Slices in Go are not thread-safe.

Direct Map Access on Thread-Safe Struct HIGH

Direct access to map fields on structs that provide thread-safe accessor methods can cause race conditions. Use the provided accessor methods instead.

Potential Race Condition MEDIUM

Shared data accessed from goroutines without synchronization.

WaitGroup Misuse HIGH

Improper use of sync.WaitGroup can cause race conditions, panics, or deadlocks. Common issues include calling Add() inside goroutines and Done() count mismatches.

🟨 Javascript 1 rules

Race Condition in Concurrent Operations HIGH

Detects time-of-check to time-of-use (TOCTOU) vulnerabilities where the state can change between checking a condition and acting on it. Common race conditions include: - Check balance, then deduct (balance can change in between) - Check inventory, then create order (stock can be sold out) - Check permissions, then perform action (permissions can change) - File existence check, then read/write (file can be modified)

🔷 Typescript 1 rules

Race Condition in Concurrent Operations HIGH

🐍 Python 1 rules

Potential Race Condition MEDIUM

Detects potential race conditions in concurrent Python code. Common race condition patterns: 1. Global variables accessed from threads without locking 2. TOCTOU (Time-of-check Time-of-use) file operations 3. Shared data structures modified in threads without synchronization 4. Check-then-act patterns without atomicity Python's GIL doesn't prevent all race conditions, especially with I/O operations and multi-process code.

4 Warning Signs

What to watch for in code reviews

These patterns indicate potential Concurrent Execution Using Shared Resource with Improper Synchronization ('Race Condition') vulnerabilities. Look for these during code reviews and security audits.

🟠

Concurrent slice access without synchronization causes data races. append() is NOT atomic - multiple goroutines appendin go-concurrent-slice-access

🟠

Direct access to map fields can cause race conditions in concurrent code. Maps in Go are not thread-safe, and concurrent go-direct-map-access

🟠

Improper WaitGroup usage can cause: - Race conditions (Add inside goroutine) - Panics (negative counter from Done miscou go-waitgroup-misuse

🟠

Race condition at ... - check and act are not atomic javascript-race-conditions

🟠

time-of-check to time-of-use (TOCTOU) vulnerabilities where the state can change between checking a javascript-race-conditions

🟡

Shared data accessed without proper synchronization go-race-condition

🟡

potential race conditions in concurrent Python code python-race-condition

🔍

Scan your codebase for Concurrent Execution Using Shared Resource with Improper Synchronization ('Race Condition')

Shoulder CLI finds vulnerable patterns across your entire codebase.

npx shoulder trust Browse all rules