Offensive Crash Analysis

SKILL: Week 4: Crash Analysis and Exploitability Assessment

Metadata

• Skill Name: crash-analysis
• Folder: offensive-crash-analysis
• Source: https://github.com/SnailSploit/offensive-checklist/blob/main/4-crash-analysis.md

Description

Week 4 exploit development curriculum. Crash triage and analysis methodology: WinDbg/GDB analysis, ASAN/MSAN output interpretation, exploitability assessment, register/stack trace reading, root cause identification. Use when analyzing crash dumps, assessing exploitability, or understanding fuzzer-generated crashes.

Trigger Phrases

Use this skill when the conversation involves any of: crash analysis, crash triage, WinDbg, GDB, ASAN, MSAN, exploitability, stack trace, register dump, segfault, null deref, access violation, week 4

Instructions for Claude

When this skill is active:

1. Load and apply the full methodology below as your operational checklist
2. Follow steps in order unless the user specifies otherwise
3. For each technique, consider applicability to the current target/context
4. Track which checklist items have been completed
5. Suggest next steps based on findings

---

Full Methodology

Week 4: Crash Analysis and Exploitability Assessment

Overview

created by AnotherOne from @Pwn3rzs Telegram channel.

After finding potential vulnerabilities through fuzzing (Week 2) or patch diffing (Week 3), the next critical step is analyzing crashes to determine if they're exploitable. This week focuses on crash triage, debugger mastery, and techniques for identifying how to reach vulnerable code paths from attacker-controlled input.

Once you've confirmed a crash is exploitable and built a PoC, you'll be ready for Basic Exploitation in Week 5.

Prerequisites

Before starting this week, ensure you have:

• A Windows VM (for WinDbg labs) and a Linux VM (for GDB/ASAN/CASR labs).
• Completed Week 2 fuzzing labs, including running AFL++ or libFuzzer against at least one C/C++ target
• Completed (or skimmed) Week 3 patch diffing labs:
• Familiar with Ghidriff/Diaphora diff reports and how to interpret changed functions
• Understand how to extract Windows updates and Linux kernel patches
• Reviewed at least one case study (CVE-2022-34718 EvilESP, CVE-2024-1086 nf_tables, or 7-Zip symlink bugs)
• Comfortable understanding from Week 1 of basic vulnerability classes (buffer overflow, UAF, integer bugs, info leaks) and their exploit primitives

Crash Analysis Decision Tree

Use this decision tree to select the appropriate tools and workflow for any crash you encounter:

┌─────────────────────────────────────────────────────────────────────┐
│                        CRASH RECEIVED                               │
└─────────────────────────────────────────────────────────────────────┘
                                │
                                ▼
                    ┌───────────────────────┐
                    │ Source code available?│
                    └───────────────────────┘
                      │                    │
                     Yes                   No
                      │                    │
                      ▼                    ▼
        ┌─────────────────────┐   ┌──────────────────────────┐
        │ Recompile with      │   │ What platform?           │
        │ ASAN + UBSAN        │   └──────────────────────────┘
        │ (Day 2)             │     │         │         │
        └─────────────────────┘     │         │         │
                      │          Windows   Linux    Mobile
                      │             │         │         │
                      ▼             ▼         ▼         ▼
        ┌─────────────────────┐ ┌───────┐ ┌───────┐ ┌───────────┐
        │ Run crash input     │ │WinDbg │ │Pwndbg │ │ Tombstone │
        │ Get detailed report │ │+ TTD  │ │+ rr   │ │ + Frida   │
        └─────────────────────┘ │(Day 1)│ │(Day 1)│ │ (Future)  │
                      │         └───────┘ └───────┘ └───────────┘
                      │             │         │         │
                      └─────────────┴────┬────┴─────────┘
                                         │
                                         ▼
                    ┌─────────────────────────────────────┐
                    │ Crash requires special environment? │
                    └─────────────────────────────────────┘
                       │                              │
                      Yes                             No
                       │                              │
                       ▼                              │
        ┌─────────────────────────────┐               │
        │ Setup reproduction env:     │               │
        │ - Network (tcpdump, proxy)  │               │
        │ - Files (strace, procmon)   │               │
        │ - Services (docker, VM)     │               │
        └─────────────────────────────┘               │
                       │                              │
                       └──────────────┬───────────────┘
                                      │
                                      ▼
                            ┌─────────────────────┐
                            │ Crash type known?   │
                            └─────────────────────┘
                              │                 │
                             Yes                No
                              │                 │
                              ▼                 ▼
                ┌─────────────────────┐  ┌─────────────────────┐
                │ Run CASR for        │  │ Manual analysis:    │
                │ classification      │  │ - Examine registers │
                │ (Day 3)             │  │ - Check memory      │
                └─────────────────────┘  │ - Disassemble       │
                              │          │ (Day 3)             │
                              │          └─────────────────────┘
                              │                 │
                              └────────┬────────┘
                                       │
                                       ▼
                          ┌─────────────────────────┐
                          │ EXPLOITABILITY ASSESS   │
                          │ - Check mitigations     │
                          │ - Control analysis      │
                          │ - Reachability (Day 4)  │
                          └─────────────────────────┘
                                       │
                                       ▼
                          ┌─────────────────────────┐
                          │ Multiple crashes?       │
                          └─────────────────────────┘
                            │                    │
                           Yes                   No
                            │                    │
                            ▼                    ▼
              ┌─────────────────────┐   ┌─────────────────────┐
              │ Deduplicate (Day 5) │   │ Minimize (Day 5)    │
              │ - CASR cluster      │   │ - afl-tmin          │
              │ - Stack hash        │   │ - Manual reduction  │
              └─────────────────────┘   └─────────────────────┘
                            │                    │
                            └────────┬───────────┘
                                     │
                                     ▼
                        ┌─────────────────────────┐
                        │ Create PoC (Day 6)      │
                        │ - Python + pwntools     │
                        │ - Verify reliability    │
                        │ - Document findings     │
                        └─────────────────────────┘

Quick Reference - Tool Selection by Scenario:

| Scenario | Primary Tool | Secondary Tool | Sanitizer | | --------------------------- | -------------------------- | ---------------- | ------------ | | Linux binary, have source | GDB + Pwndbg | rr | ASAN + UBSAN | | Linux binary, no source | GDB + Pwndbg | Ghidra | N/A | | Windows binary, have source | WinDbg + TTD | Visual Studio | ASAN | | Windows binary, no source | WinDbg + TTD | IDA/Ghidra | N/A | | Fuzzer crash corpus | CASR | afl-tmin | ASAN | | Non-deterministic crash | rr (Linux) / TTD (Windows) | Chaos mode | TSAN | | Kernel crash (Linux) | crash utility | GDB + KASAN | KASAN | | Kernel crash (Windows) | WinDbg kernel | Driver Verifier | N/A | | Android app crash | Tombstone + ndk-stack | Frida | HWASan | | Rust/Go crash | Native debugger | Sanitizer output | Built-in |

Day 1: Debugger Fundamentals and Crash Dump Analysis

• Goal: Learn Windows Debugger (WinDbg) and Linux debugger (GDB + Pwndbg) for analyzing application crashes.
• Activities:
• Reading:
• "Practical Malware Analysis" by Michael Sikorski - Chapter 9 and 10
• WinDbg Official Documentation
• Pwndbg Documentation
• Online Resources:
• Common WinDbg Commands
• Debugging Tools for Windows
• GDB Quick Reference
• Tool Setup:
• Windows: Install WinDbg Preview from Microsoft Store
• Linux: Install GDB with Pwndbg enhancement
• Install Windows SDK for symbol support
• Exercise:
• Analyze 5 pre-generated crash dumps (Windows and Linux)
• Identify crash type and root cause for each

Reproduction Fidelity

> [!IMPORTANT] > Before any crash analysis, ensure you can reproduce the crash reliably. > A crash that only happens "sometimes" or "on the fuzzer's machine" is nearly impossible to analyze or exploit. > This section establishes the mandatory checklist for achieving reproduction fidelity.

Reproduction Fidelity Checklist

Before analyzing any crash, verify these match between discovery and analysis environments:

┌─────────────────────────────────────────────────────────────────┐
│ REPRODUCTION FIDELITY CHECKLIST                                 │
├─────────────────────────────────────────────────────────────────┤
│ System Environment                                              │
│ [ ] OS/Kernel version     : ________________________________    │
│ [ ] libc version          : ________________________________    │
│ [ ] CPU architecture      : [ ] x86 [ ] x86_64 [ ] ARM64        │
│ [ ] Container/VM          : [ ] Native [ ] Docker [ ] VM        │
│ [ ] ASLR state            : [ ] Enabled [ ] Disabled            │
├─────────────────────────────────────────────────────────────────┤
│ Process Environment                                             │
│ [ ] argv (command-line)   : ________________________________    │
│ [ ] Environment variables : ________________________________    │
│ [ ] Working directory     : ________________________________    │
│ [ ] Locale (LC_ALL, LANG) : ________________________________    │
│ [ ] umask / permissions   : ________________________________    │
├─────────────────────────────────────────────────────────────────┤
│ Input Path                                                      │
│ [ ] Input source          : [ ] stdin [ ] file [ ] network      │
│ [ ] Input file path       : ________________________________    │
│ [ ] Network port/protocol : ________________________________    │
├─────────────────────────────────────────────────────────────────┤
│ Build Configuration                                             │
│ [ ] Compiler version      : ________________________________    │
│ [ ] Optimization level    : [ ] -O0 [ ] -O1 [ ] -O2 [ ] -O3     │
│ [ ] Sanitizers            : [ ] ASAN [ ] UBSAN [ ] TSAN [ ] None│
│ [ ] Debug symbols         : [ ] Yes [ ] No                      │
│ [ ] Mitigations           : [ ] PIE [ ] Canary [ ] RELRO        │
└─────────────────────────────────────────────────────────────────┘

Essential Environment Knobs

ASAN/UBSAN Options (Linux/macOS):

# Full ASAN options for crash analysis
export ASAN_OPTIONS="\
abort_on_error=1:\
symbolize=1:\
detect_leaks=1:\
disable_coredump=0:\
halt_on_error=1:\
print_stats=1:\
check_initialization_order=1:\
detect_stack_use_after_return=1:\
quarantine_size_mb=256"

# UBSAN options
export UBSAN_OPTIONS="\
print_stacktrace=1:\
halt_on_error=1:\
suppressions=ubsan_suppressions.txt"

# Symbolizer path (required for readable stack traces)
export ASAN_SYMBOLIZER_PATH=$(command -v llvm-symbolizer)

glibc Allocator Tuning (Linux):

# Enable glibc heap consistency checks (catch corruption early)
export MALLOC_CHECK_=3

# Modern glibc tunable interface (glibc 2.26+)
export GLIBC_TUNABLES="\
glibc.malloc.check=3:\
glibc.malloc.perturb=165"

# What these do:
# MALLOC_CHECK_=3: Abort on heap corruption detection
# glibc.malloc.perturb=165: Fill freed memory with 0xA5 (helps detect UAF)

Core Dump Configuration (Linux):

# Enable unlimited core dumps
ulimit -c unlimited

# Verify core pattern (where dumps go)
cat /proc/sys/kernel/core_pattern

# For local dumps in CWD (temporary, affects system):
# echo 'core.%e.%p' | sudo tee /proc/sys/kernel/core_pattern

ASLR Control (Linux - for deterministic analysis):

# Check current ASLR state
cat /proc/sys/kernel/randomize_va_space
# 0 = disabled, 1 = conservative, 2 = full

# Disable ASLR for current shell (temporary, per-process)
setarch $(uname -m) -R ./target /dev/null
    EXIT_CODE=$?

    # Check for crash signal (128 + signal number)
    if [ $EXIT_CODE -gt 128 ]; then
        SIGNAL=$((EXIT_CODE - 128))
        if [ $SIGNAL -eq $EXPECTED_SIGNAL ] || [ $SIGNAL -eq 6 ]; then
            ((CRASHES++))
        fi
    fi
done

echo "[*] Crash rate: $CRASHES/10"
if [ $CRASHES -ge 9 ]; then
    echo "[+] Reproduction: RELIABLE"
elif [ $CRASHES -ge 5 ]; then
    echo "[!] Reproduction: FLAKY - investigate environment"
else
    echo "[-] Reproduction: FAILED - check environment checklist"
fi

Installing WinDbg and Symbol Support

WinDbg Preview (recommended - modern UI):

winget install Microsoft.WinDbg

Windows SDK Debugging Tools (includes cdb.exe for command-line/batch analysis):

# Option 1: Install via winget (Windows SDK)
winget install --source winget --exact --id Microsoft.WindowsSDK.10.0.26100

# Option 2: Download from Microsoft
# https://developer.microsoft.com/en-us/windows/downloads/windows-sdk/
# During installation, select "Debugging Tools for Windows"

# After installation, cdb.exe is located at:
# C:\Program Files (x86)\Windows Kits\10\Debuggers\x64\cdb.exe

# Add to PATH for convenience (run as Administrator):
setx PATH "%PATH%;C:\Program Files (x86)\Windows Kits\10\Debuggers\x64" /M

# Or use full path in scripts:
"C:\Program Files (x86)\Windows Kits\10\Debuggers\x64\cdb.exe" -z dump.dmp -c "!analyze -v; q"

Configure Symbol Path:

# In WinDbg Settings -> Default Symbol Path, or:
# In WinDbg command window:
.sympath SRV*C:\Symbols*https://msdl.microsoft.com/download/symbols

# Or set environment variable permanently (recommended):
setx _NT_SYMBOL_PATH "SRV*C:\Symbols*https://msdl.microsoft.com/download/symbols"

# Create symbols cache directory
mkdir C:\Symbols

# Reload symbols (in debugger)
.reload /f

Linux Crash Dump Generation and Pwndbg Setup

> [!HINT] > While Windows uses WinDbg, Linux crash analysis uses GDB enhanced with Pwndbg. This section covers parallel

…

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: SnailSploit
• Source: SnailSploit/Claude-Red
• License: MIT

Install and usage instructions live in the source repository linked above.