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CVE-2025-31133 — runC Container Runtime Container Escape

Key facts

CVE-2025-31133 is a High (8.6) vulnerability: runC Container Runtime Container Escape. This entry ships a detection-only PoC.
CVE CVE-2025-31133
Severity High (8.6)
Detection / prevention —
PoC poc.py
Source 2025/CVE-2025-31133/

Details

CVSS Type

Overview

Attribute Value
CVE ID CVE-2025-31133
Severity High
CVSS Score 8.6
Affected Product runC Container Runtime
Vulnerability Type Container Escape
CWE CWE-59

Description

Container escape vulnerability in runC's maskedPaths feature. Attackers replace /dev/null with symbolic link during container creation to mount arbitrary host paths.

Affected Versions

  • runC < 1.2.8, < 1.3.3, < 1.4.0-rc.3

Verification Process

The PoC uses a multi-stage verification approach:

Step 1: Product/Version Detection (Passive)

[*] Query target endpoint
[*] Detect product signatures and extract version
[*] Check if version is in vulnerable range

Step 2: Active Vulnerability Testing

Method Description Detection
Error-based Inject payloads that trigger error messages Error indicators in response
Timing-based Inject delay commands and measure response Response time > baseline + delay
Response-based Check for expected patterns in response Pattern match in response body
Callback-based Trigger OOB request to attacker server HTTP request received

Verification Flow

┌─────────────────────────────────────────────────────────────┐
│                    Product Detection                         │
│  Query target → Detect product/version                      │
│  Check if version in vulnerable range                       │
└─────────────────────────────────────────────────────────────┘
                              ↓
┌─────────────────────────────────────────────────────────────┐
│               Active Vulnerability Testing                   │
│                                                              │
│  1. Error-based Test                                         │
│     └─ Send payload → Check for error indicators            │
│     └─ If error found → CONFIRMED VULNERABLE                │
│                                                              │
│  2. Timing-based Test                                        │
│     └─ Send delay payload → Measure response time           │
│     └─ If delayed → CONFIRMED VULNERABLE                    │
│                                                              │
│  3. Callback-based Test (if URL provided)                    │
│     └─ Send OOB payload → Check callback server             │
│     └─ If request received → CONFIRMED VULNERABLE           │
└─────────────────────────────────────────────────────────────┘

Usage

# Full vulnerability check (version + active testing)
python3 poc.py -t https://target.com -c

# Version-only check (passive, no payloads sent)
python3 poc.py -t https://target.com -c --version-only

# With OOB callback (most reliable)
python3 poc.py -t https://target.com -c --callback http://your-server.com

Mitigation

  1. Upgrade to the latest patched version
  2. Apply workarounds if patch unavailable
  3. Monitor for exploitation attempts
  4. Network segmentation to limit exposure

References

Frequently asked questions

What is CVE-2025-31133?

CVE-2025-31133 is a High (8.6) vulnerability: runC Container Runtime Container Escape. This entry ships a detection-only PoC.

How do I detect CVE-2025-31133?

Run the detection-only PoC included with this entry against your Docker test lab to confirm whether a target is affected; pair it with your own IDS logging.

How do I block or mitigate CVE-2025-31133?

Upgrade to a fixed version per the vendor advisory; the NVD record lists the affected versions. Use the included PoC to verify your remediation.

For authorized security testing and research only. See the full source and NVD record.