How to Hack AWS S3 Buckets (Ethically) 2026 — 5 Real Misconfigurations Exposed
Mr Elite ··
16 min read
⚠️ Ethical Testing Only: Only test S3 buckets belonging to domains within an explicit bug bounty programme scope or your own AWS account. Accessing private buckets without authorisation violates the Computer Fraud and Abuse Act regardless of misconfiguration. Never exfiltrate sensitive data even from publicly accessible buckets. This guide is for security education and authorised testing only.
The easiest Critical-severity finding in cloud security bug bounty 2026 does not require any exploit. It does not need a zero-day or special tools. It requires knowing what to search for, a free AWS CLI installation, and five minutes. Hundreds of companies — including Fortune 500 organisations — still have S3 buckets misconfigured with public access, exposing internal documents, database backups, API keys, and customer PII to anyone who knows the bucket name. Today I am showing you the five real misconfiguration types that pay in bug bounty, how to find them ethically, and exactly what to do when you find one Lets start our session on How to Hack AWS S3 Buckets Ethically.
🎯 What You’ll Master in This Guide
Understand the 5 S3 misconfiguration types that pay real money in bug bounty
Enumerate S3 buckets linked to a target company using passive and active techniques
Test bucket permissions with AWS CLI without any credentials
Identify and report S3 bucket takeover vulnerabilities via unclaimed subdomains
Write a cloud security bug bounty report that accurately conveys impact and gets paid
⏱️ 46 min read · 3 hands-on exercises
📊 What is your cloud security testing experience?
✅ Cloud security has become one of the highest-value bug bounty categories. Whether you are starting from zero or looking for advanced bucket takeover techniques, this guide covers the full spectrum from passive enumeration to Critical-severity reporting.
📋 What You’ll Master — How to Hack AWS S3 Buckets Ethically 2026
S3 security fits within the broader Bug Bounty Mastery Course because it represents a category where recon skills translate directly into high-severity findings — no exploitation required. The same subdomain enumeration and passive recon techniques you learned earlier in the course are the primary discovery methods for S3 targets. If you want to understand how cloud security fits into penetration testing methodology more broadly, the concepts here apply across AWS, Azure, and GCP storage services.
Why AWS S3 Misconfigurations Still Pay Critical in 2026
AWS introduced Block Public Access settings in 2018 and made them default for new buckets in 2023. Despite this, millions of pre-existing buckets were created before these controls existed, and many organisations have never audited their legacy cloud storage. S3 misconfigurations continue to cause some of the largest data breaches in history — Capital One (106 million records), GoDaddy (1.2 million customer records), and dozens of others each year.
The reason these findings command Critical-severity ratings is not the misconfiguration itself — it is what is in the bucket. A public bucket containing only marketing images is a Low finding. The same misconfiguration on a bucket containing database backups, source code with hardcoded API keys, or customer PII becomes Critical immediately. Your job as a bug bounty hunter is to identify the misconfiguration and assess what it exposes.
Public bucket with only public assets (images, CSS, fonts)
$0–$200
📸 S3 misconfiguration severity matrix — the payout depends on what is exposed, not just whether the bucket is public. Impact assessment is the critical skill.
S3 Bucket Enumeration — Finding Targets Without Brute Force
Passive enumeration finds S3 buckets linked to a target without sending a single packet to their servers. This is the safest and most efficient starting point.
S3 BUCKET ENUMERATION — PASSIVE AND ACTIVE METHODS
# Method 1: GrayhatWarfare — search public buckets by keyword (browser)
https://buckets.grayhatwarfare.com/
# Search: company name, product name, domain keyword
# Method 2: Find S3 bucket references in page source
subfinder -d target.com -silent | while read sub; do dig CNAME $sub | grep s3; done
🛠️ EXERCISE 1 — BROWSER (10 MIN · NO INSTALL)
Find Public S3 Buckets Linked to a Real Company Using GrayhatWarfare
⏱️ Time: 10 minutes · Browser only
Step 1: Go to buckets.grayhatwarfare.com (free tier available)
Step 2: Search for a keyword related to any company you are
researching (use a company from a public bug bounty programme)
Step 3: Review the results — for each bucket shown, note:
– The bucket name
– File types present (look for: .env, .sql, .bak, .json, .csv)
– Approximate file count
– Whether it appears to be production or testing data
Step 4: Open your browser developer tools (F12 > Network tab)
Step 5: Visit any large tech company’s website that has a bug bounty
Step 6: Watch for s3.amazonaws.com requests in the Network panel
Step 7: Note the bucket names referenced — these are legitimate
recon targets within that programme’s scope
IMPORTANT: Do NOT download or access any files you find.
This exercise is observation only.
✅ What you just learned: GrayhatWarfare is a passive intelligence tool — it indexes publicly accessible S3 buckets so you can search without making any requests directly to the target. The Network panel exercise shows you that bucket names are frequently exposed in normal page loads, making them trivial to find for any company with a bug bounty programme. This passive phase takes 10 minutes and often identifies more targets than hours of active scanning.
📸 Screenshot the GrayhatWarfare search results (with sensitive info redacted) and share in #cloud-security on Discord.
AWS S3 Misconfiguration Testing — Checking Permissions With AWS CLI
AWS CLI S3 PERMISSION TESTING (NO CREDENTIALS REQUIRED FOR PUBLIC CHECKS)
# Install AWS CLI on Kali
sudo apt install awscli -y
# Test public read access (no credentials needed for public buckets)
aws s3 ls s3://TARGET-BUCKET-NAME –no-sign-request
# If returns file listing — bucket has public read access
2024-01-15 14:23:11 1234 backup.sql
2024-02-01 09:11:45 432100 database_export.csv
# Test public write access (creates a test file — only in authorised scope)
The 5 S3 Misconfigurations That Pay in Bug Bounty (With PoC Methods)
1. Public Read on Sensitive Data: The bucket is publicly readable and contains files that should be private — .env files, database exports, source code, or customer records. Proof: aws s3 ls s3://bucket –no-sign-request returns file listing. Impact increases dramatically if sensitive files are present.
2. Public Write Access: Unauthenticated users can upload files to the bucket. If the bucket serves content on a company domain, this allows hosting phishing pages or malicious JavaScript under a trusted domain. Always delete any test files you create immediately after confirmation.
3. Any Authenticated AWS User Policy: Bucket policy grants access to Principal: “*” with Condition requiring only AWS authentication — meaning any of Amazon’s 300 million+ users can access the bucket. This is more dangerous than it sounds: create a free AWS account and suddenly have access to “private” corporate data.
4. Exposed Credentials in Bucket Files: During passive enumeration, a publicly readable bucket contains .env, config.json, or terraform.tfstate files with AWS access keys, database passwords, or API credentials. These escalate immediately to Critical — the credential exposure is the vulnerability, not the bucket misconfiguration.
5. Bucket Takeover: A DNS CNAME points to a deleted S3 bucket. Anyone can register the same bucket name and serve content under the company’s subdomain. This is the most consistently Critical-rated S3 finding in bug bounty programmes in 2026.
🧠 EXERCISE 2 — THINK LIKE A HACKER (8 MIN · NO TOOLS)
What Would You Do if You Found an S3 Bucket With a Database Export?
⏱️ Time: 8 minutes · No tools required
Scenario: You are testing a bug bounty target. Using GrayhatWarfare,
you find a public S3 bucket named company-prod-backups. Running:
aws s3 ls s3://company-prod-backups –no-sign-request
1. You can see the filenames. Should you download the .env file
to confirm it contains credentials? Why or why not?
2. How do you estimate the severity rating WITHOUT accessing file
contents — what does the file naming alone tell you?
3. What is the minimal evidence you need for a valid bug bounty
report, without downloading any sensitive data?
4. The company does not have a security.txt or bug bounty programme
listed. You found customer data exposed. What do you do?
✅ What you just learned: The filenames alone — users_full_export, orders_backup, .env — are sufficient to assign Critical severity. You do not need to download the database to prove the finding. List the accessible filenames, include the aws s3 ls output as your PoC, and describe the potential impact of each file type. Downloading sensitive data is unnecessary, risky legally, and likely to cause ethical issues. The finding is the misconfiguration plus the file types visible — not the file contents.
📸 Write your analysis and share in #cloud-security on Discord.
S3 Bucket Takeover — The Highest-Paying Cloud Finding of 2026
Bucket takeover is consistently one of the highest-severity findings in cloud security bug bounty. The vulnerability is simple: a company creates an S3 bucket, points a subdomain CNAME at it, then deletes the bucket — but forgets to remove the DNS record. Now anyone can create a bucket with the same name and their content serves under the company’s subdomain.
S3 BUCKET TAKEOVER DETECTION WORKFLOW
# Step 1: Enumerate subdomains of target
subfinder -d target.com -silent -o subdomains.txt
# Step 2: Check each subdomain’s CNAME for S3 pointers
cat subdomains.txt | while read sub; do dig CNAME $sub +short | grep -i s3 && echo “[S3-CNAME] $sub”; done
# Step 5: Report the finding — DO NOT register the bucket yourself
# In bug bounty: the NoSuchBucket PoC + CNAME evidence is sufficient proof
⚠️ Do Not Register the Bucket: When you find a bucket takeover vulnerability, do NOT register the bucket yourself to “prove” the finding. Registering gives you control of a company’s subdomain without authorisation — which is itself a legal grey area even with bug bounty intent. The NoSuchBucket error plus the CNAME record is sufficient proof for any programme. Report it and let the company fix it.
🌐 EXERCISE 3 — TRYHACKME (25 MIN)
Explore AWS S3 Security Misconfigurations in a Controlled Lab Environment
Step 1: Go to tryhackme.com and search for “AWS” or “Cloud Security”
Look for rooms: “CloudGoat” or “AWS Basics” (free rooms available)
Step 2: If CloudGoat is unavailable, use the DVWA equivalent for cloud:
flaws.cloud — this is an intentionally vulnerable AWS environment
designed specifically for learning S3 security (completely free)
Step 3: Go to flaws.cloud in your browser
Read the first challenge description
Step 4: Follow the hints to enumerate the S3 bucket behind flaws.cloud
aws s3 ls s3://flaws.cloud –no-sign-request
Step 5: List the files you find — what level of access does the bucket have?
Step 6: Complete as many levels as you can in 25 minutes
Each level teaches a different S3/AWS misconfiguration type
Step 7: For each level, document:
– The misconfiguration type
– How you discovered it
– What data was exposed
– The severity rating you would assign
✅ What you just learned: flaws.cloud is built specifically to teach AWS security misconfigurations in a hands-on environment with real AWS infrastructure. The bucket enumeration, permission testing, and credential exposure scenarios you practice here are identical to what you will encounter in real bug bounty programmes. Each level of flaws.cloud maps directly to a real-world finding type — complete all six levels and you will have hands-on experience with every major S3 vulnerability class.
📸 Screenshot your flaws.cloud progress and share in #cloud-security on Discord.
Cloud Security Bug Bounty — Writing the Report and Getting Paid
S3 misconfiguration reports get rejected or downgraded for one common reason: the reporter lists the misconfiguration without demonstrating impact. “The bucket is publicly readable” alone is a Low finding. “The bucket is publicly readable and contains a file named users_export_2026.sql.gz, indicating potential customer PII exposure at scale” is a Critical finding. The words “indicating potential” are important — you are assessing impact based on evidence, not downloading the data to prove it.
Your report structure for S3 findings should follow this order: bucket URL and permission test result (your aws s3 ls output), CNAME or reference source showing it belongs to the target, file listing with analysis of what each file type suggests about the data’s sensitivity, impact statement describing what a malicious actor could accomplish, and a clear remediation recommendation (enable Block Public Access, review and delete unnecessary public buckets, implement least-privilege bucket policies).
🧠 QUICK CHECK — S3 Security
You run aws s3 ls s3://company-prod --no-sign-request and receive a NoSuchBucket error. However, dig CNAME static.company.com returns static.company.com CNAME company-prod.s3.amazonaws.com. What vulnerability does this indicate?
📋 Key Tools — S3 Security Testing Reference
aws s3 ls s3://BUCKET –no-sign-requestTest public read access — lists bucket contents without credentials
curl -s https://BUCKET.s3.amazonaws.com | grep NoSuchBucketDetect bucket takeover — NoSuchBucket error on live CNAME = vulnerable
dig CNAME subdomain.target.comFind S3 CNAME records — look for s3.amazonaws.com in output
buckets.grayhatwarfare.comPassive public bucket search — find exposed buckets by company keyword
flaws.cloudFree intentionally vulnerable AWS lab — practice all S3 misconfigs safely
❓ Frequently Asked Questions
Is it legal to test AWS S3 buckets for misconfigurations?
You can legally access publicly accessible S3 buckets — they are configured to be public. However, accessing buckets requiring authentication without authorisation may violate computer fraud laws. For bug bounty, only test S3 buckets belonging to domains within the programme’s explicit scope. Never download large amounts of data or access clearly private information even from misconfigured public buckets.
What is an S3 bucket takeover and how does it work?
Bucket takeover occurs when a company has a DNS CNAME pointing to a deleted S3 bucket. Anyone can create a bucket with that name and their content serves under the company’s subdomain. This allows serving phishing pages, malicious JavaScript, or misleading content under a trusted domain. It is consistently rated High or Critical in bug bounty programmes.
Which tools are used for S3 bucket enumeration?
Primary tools in 2026: AWS CLI for permission testing, GrayhatWarfare for passive bucket discovery, S3Scanner for automated permission testing, Subfinder/Amass for subdomain-based bucket reference discovery, and flaws.cloud for hands-on practice. Combining GrayhatWarfare for passive discovery with AWS CLI for active permission testing covers most bug bounty scenarios.
How much do S3 misconfiguration findings pay in bug bounty?
Payouts range from nothing (public assets only) to $30,000+ (credentials exposed or PII breach). Public write access typically pays High ($1k–$5k). Bucket takeover pays High to Critical ($1k–$10k). Exposed credentials in bucket files leading to account compromise pays Critical ($5k–$30k+). The payout depends almost entirely on what is exposed, not just whether the bucket is public.
What should I do if I find sensitive data in a public S3 bucket?
Stop accessing the bucket after confirming the finding. Do not download data beyond what proves the misconfiguration. Document the bucket name, file listing, and impact assessment. Report through the bug bounty programme. If no disclosure channel exists and active harm appears imminent, consider contacting the company directly via their security contact email or abuse@company.com.
How do companies accidentally expose S3 buckets?
Common causes: buckets created with public ACL during testing and forgotten, infrastructure-as-code templates from tutorials with public ACL settings, accidental .env uploads during CI/CD deployments, legacy buckets created before AWS Block Public Access existed, and cross-account policy mistakes. Since 2023, AWS enables Block Public Access by default on new buckets, but millions of older buckets predate this.
SSRF Bug Bounty 2026— Day 10 covers Server-Side Request Forgery, including AWS metadata endpoint attacks that complement S3 security testing in cloud bug bounty programmes.
Bug Bounty Recon Techniques— The complete recon methodology covering subdomain enumeration, JavaScript analysis, and passive intelligence gathering techniques used to find S3 targets.
60-Day Bug Bounty Mastery Course— The full course hub from beginner recon through advanced vulnerability chaining with the cloud security modules in the later days.
flaws.cloud — Intentionally Vulnerable AWS Lab— A free, completely legal AWS security training environment designed specifically to teach S3 misconfigurations and AWS attack techniques through hands-on challenges.
AWS S3 Security Best Practices— The official AWS documentation for S3 security covering Block Public Access, bucket policies, ACL management, and encryption — essential reading for both attackers and defenders.
ME
Mr Elite
Owner, SecurityElites.com
The most unsettling S3 finding I ever reported was a publicly readable bucket that contained the entire infrastructure-as-code repository of a large healthcare company — including Terraform state files with production database passwords, API keys for three payment processors, and SSH private keys for their production servers. Nobody had accessed it maliciously as far as anyone could determine. It had been public for 11 months. The file had been uploaded by a junior developer who thought the bucket was internal. The company paid Critical severity, fixed it within hours, and rotated every credential in the state file. That one discovery required five minutes of passive recon and zero exploitation. Cloud misconfigurations are the fastest path to Critical findings in bug bounty for exactly this reason.
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