Exploit for Use After Free in Linux Linux_Kernel CVE-2026-23111

## https://sploitus.com/exploit?id=36DF04B9-37D6-5EC9-8C27-E6A68CEFEB6D
# 🐧 CVE-2026-23111 - Linux Kernel nf_tables Use-After-Free Vulnerability



![Severity](https://img.shields.io/badge/Severity-High-orange?style=for-the-badge)
![CVSS](https://img.shields.io/badge/CVSS-7.8-red?style=for-the-badge)
![CWE](https://img.shields.io/badge/CWE-416-yellow?style=for-the-badge)
![Platform](https://img.shields.io/badge/Linux-Kernel-blue?style=for-the-badge)

### ⚠️ Use-After-Free in Linux Kernel nf_tables



---

## 📖 Overview

**CVE-2026-23111** is a high-severity **Use-After-Free (UAF)** vulnerability affecting the Linux kernel's **netfilter/nf_tables** subsystem.

The flaw originates from incorrect handling of catch-all map elements during nftables transaction rollback operations, resulting in a memory safety issue that may allow local attackers to trigger kernel memory corruption.

---

## 🎯 Vulnerability Information

| Field | Value |
|---------|---------|
| CVE | CVE-2026-23111 |
| Severity | High |
| CVSS v3.1 | 7.8 |
| CWE | CWE-416 |
| Vulnerability Type | Use After Free |
| Attack Vector | Local |
| Privileges Required | Low |
| User Interaction | None |
| Component | netfilter / nf_tables |
| Exploitation Complexity | Low |

---

## 🔬 Technical Analysis

The vulnerability exists in:

```text
net/netfilter/
            └── nf_tables
```

During rollback of a failed transaction, the function:

```c
nft_map_catchall_activate()
```

contains an inverted generation-mask validation logic.

This causes the kernel to incorrectly reactivate catch-all map elements, potentially resulting in references to memory that has already been freed.

Consequences include:

- Memory corruption
- Kernel crashes
- Denial of Service
- Potential privilege escalation

---

## ⚡ Attack Flow

```text
┌─────────────────────┐
│ Local Attacker      │
└──────────┬──────────┘
           │
           ▼
┌─────────────────────┐
│ nftables Operation  │
└──────────┬──────────┘
           │
           ▼
┌─────────────────────┐
│ Transaction Failure │
└──────────┬──────────┘
           │
           ▼
┌─────────────────────┐
│ Rollback Triggered  │
└──────────┬──────────┘
           │
           ▼
┌───────────────────────────┐
│ nft_map_catchall_activate │
│ Logic Error               │
└──────────┬────────────────┘
           │
           ▼
┌─────────────────────┐
│ Use-After-Free      │
│ Condition           │
└──────────┬──────────┘
           │
           ▼
┌─────────────────────┐
│ Memory Corruption   │
└──────────┬──────────┘
           │
           ▼
┌─────────────────────┐
│ Kernel Compromise   │
└─────────────────────┘
```

---

## 🧠 Root Cause

### Expected Behavior

```text
Rollback
   │
   ▼
Reactivate Inactive Elements
```

### Actual Behavior

```text
Rollback
   │
   ▼
Incorrect Generation Check
   │
   ▼
Invalid Element Activation
   │
   ▼
Use-After-Free
```

---

## 💥 Potential Impact

### Confidentiality

```text
🟠 Medium
```

Potential exposure of kernel memory.

### Integrity

```text
🔴 High
```

Memory corruption may allow modification of kernel structures.

### Availability

```text
🔴 High
```

Kernel panic and system crashes are possible.

### Privilege Escalation

```text
🔴 High
```

Local attackers may leverage the flaw to gain elevated privileges.

---

## 📦 Affected Component

```text
Linux Kernel
      │
      ▼
  Netfilter
      │
      ▼
   nf_tables
      │
      ▼
Catch-all Map Elements
```

---

## 🔍 Detection

Monitor systems for:

- Unexpected kernel crashes
- nftables failures
- Kernel warnings
- Memory corruption alerts
- Abnormal netfilter behavior
- Privilege escalation attempts

Useful logs:

```bash
dmesg
journalctl -k
audit.log
```

---

## 🛡️ Mitigation

### Recommended Actions

```bash
✓ Update Linux Kernel
✓ Apply Vendor Security Patches
✓ Restrict Local Access
✓ Monitor Kernel Logs
✓ Audit nftables Configurations
✓ Enable Security Monitoring
```

### Verification

Check kernel version:

```bash
uname -r
```

Check nftables:

```bash
nft list ruleset
```

---

## 📊 Risk Matrix

| Category | Risk |
|-----------|--------|
| Exploitability | 🟠 Medium |
| Privilege Escalation | 🔴 High |
| Denial of Service | 🔴 High |
| Memory Corruption | 🔴 High |
| Remote Exploitation | 🟢 No |
| Local Exploitation | 🔴 Yes |

---

## 📅 Timeline

| Event | Status |
|---------|---------|
| Vulnerability Discovered | ✅ |
| CVE Assigned | ✅ |
| Public Disclosure | ✅ |
| Kernel Fix Released | ✅ |
| Vendor Advisories Published | ✅ |

---

## 🔐 Security Recommendations

```text
Patch Immediately
        │
        ▼
Monitor Systems
        │
        ▼
Audit nftables Usage
        │
        ▼
Restrict Untrusted Users
        │
        ▼
Maintain Kernel Updates
```

---

## 📚 References

- Linux Kernel Security Advisories
- NVD Database
- Vendor Security Bulletins
- Linux Kernel Commit History

---



## 🚨 Security Notice

**CVE-2026-23111** demonstrates how subtle logic errors in kernel memory management can lead to serious security consequences.

### Patch Early • Monitor Continuously • Secure Your Infrastructure

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