Sudo “Chroot to Root” — Critical Library Loading Privilege Escalation

Published : Sept 23, 2025 | by : Opt

Executive Summary

Risk Level : Critical (CVSS 9.3) — However : High Risk in Enterprise Environments
Immediate Action Required : Yes — Emergency patching within 24–48 hours

CVE-2025–32463 allows local attackers to escalate privileges to root by exploiting sudo’s chroot functionality to load malicious libraries during privilege evaluation. Unlike most sudo vulnerabilities, this flaw requires no existing sudo privileges to exploit, making it exceptionally dangerous across all affected Linux/Unix systems.

Bottom Line: Any local user can become root by tricking sudo into loading attacker-controlled libraries from fake chroot environments — a textbook local privilege escalation with devastating impact.

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Vulnerability Overview

Attribute Details :
CVE ID : CVE-2025–32463
CVSS Score : 9.3 (Critical)
Affected Software : Sudo versions 1.9.14 through 1.9.17
Vulnerability Type : CWE-269: Improper Privilege Management
Discovery Date : June 2025
Public Disclosure : June 30, 2025
Patch Available : ✔️ v1.9.17p1 (June 30, 2025)
Exploited in Wild : Active scanning detected

Impact Assessment

Affected Systems

• Primary Targets : All Linux/Unix systems running sudo 1.9.14–1.9.17
• Attack Vector : Local
• Authentication Required : No — Any local user account sufficient
• User Interaction : Not Required

Business Impact

• Confidentiality : Critical — Complete system access and data exposure
• Integrity : Critical — Full root privileges enable system-wide modifications
• Availability : High — Potential for ransomware deployment and system destruction

Real-World Context

• Deployment Prevalence : Extremely high — sudo installed by default on virtually all Linux/Unix systems
• Exploitation Difficulty : Easy — Straightforward exploitation with public PoC available
• Prerequisites : Local access only — no existing sudo privileges required

Technical Analysis

Root Cause

Starting with sudo version 1.9.14, sudo began resolving paths via chroot() during policy evaluation. This created a critical window where privilege checks occurred within an attacker-controlled environment, allowing malicious NSS (Name Service Switch) libraries to be loaded with root privileges before security policies were properly enforced.

Attack Scenario

Prerequisites :

• Local access to target system
• Ability to create files in world-writable directories (/tmp)
• No sudo privileges required — this is the critical differentiator

Attack Steps :

1. Environment Setup : Create fake chroot directory with controlled /etc/nsswitch.conf
2. Library Injection : Place malicious NSS library in fake environment’s lib directory
3. Exploitation : Execute sudo -R /path/to/fake_chroot <command>
4. Root Access : Malicious library executes with root privileges during NSS lookup

Code Example

# Vulnerable exploitation pattern (1.9.14-1.9.17)
# Step 1: Create malicious environment
mkdir -p /tmp/evil_chroot/{etc,lib}
echo "passwd: files nss" > /tmp/evil_chroot/etc/nsswitch.conf

# Step 2: Place malicious NSS library (simplified example)
cp /path/to/malicious_lib.so /tmp/evil_chroot/lib/libnss_passwd.so.2
# Step 3: Trigger privilege escalation
sudo -R /tmp/evil_chroot whoami
# Result: Malicious library loads as root, grants shell
# Secure implementation (Post-Patch)
sudo -R /tmp/evil_chroot whoami
# Error: sudo: you are not permitted to use the -R option

Detection

Log Signatures

# Primary indicators - Check for suspicious chroot usage
grep -E "sudo.*(-R |--chroot)" /var/log/auth.log
journalctl -u sudo | grep -E "(chroot|--chroot|-R)"

# Secondary indicators - Monitor directory creation patterns
auditctl -w /tmp -p wa -k tmp_monitor
ausearch -k tmp_monitor | grep -E "(etc|lib)"
# Tertiary indicators - NSS library loading from unusual paths
grep -E "libnss.*\.so" /var/log/syslog | grep -v "/lib"

SIEM Detection Rule

-- Detection query (Splunk/Elastic syntax)
index=linux source="/var/log/auth.log" OR source="journald"
| search "sudo" AND ("-R " OR "--chroot ")
| rex field=_raw "PWD=(?<working_dir>[^\s;]+)"
| rex field=_raw "COMMAND=(?<command>.*)"
| where match(working_dir, "/tmp") OR match(working_dir, "/var/tmp")
| stats count by user, host, working_dir, command
| where count > 0

-- Monitor suspicious directory patterns
index=linux sourcetype=auditd type=SYSCALL syscall=mkdir
| search name="/tmp/*" AND (name="*/etc" OR name="*/lib")
| eventstats count as dir_count by uid
| where dir_count >= 2

Network/Host Indicators

• Process : Sudo processes with -R flag from non-root users
• Files : Rapid creation of /etc and /lib subdirectories in /tmp
• Libraries : .so files being created in temporary directories
• Audit : NSS library loading events from non-standard paths

Response Actions

Immediate (0–24 hours)

1. Inventory : Identify all systems running sudo 1.9.14–1.9.17 using sudo -V | head -1
2. Assess : Search logs for exploitation attempts using detection signatures
3. Isolate : If exploitation detected, immediately isolate affected systems

Short-term (1–7 days)

1. Patch: Emergency deployment of sudo 1.9.17p1+ across all infrastructure
2. Monitor: Deploy SIEM rules and enable comprehensive audit logging
3. Harden: Mount /tmp with nosuid,nodev,noexec where operationally feasible

Long-term (1+ weeks)

1. Review: Audit sudoers configurations for unnecessary chroot permissions
2. Disable: Add Defaults !use_chroot to /etc/sudoers globally
3. Test: Include privilege escalation testing in regular security assessments

Mitigation Strategies

Patch Impact Overview :

Version :1.9.14–1.9.17 ❌ → 1.9.17p1+ ✔️
Chroot Evaluation : During policy check ❌ → After policy check ✔️
Library Loading : Attacker-controlled ❌ → System-controlled ✔️
Root Exploit : Any user can exploit ❌ → Blocked ✔️
Risk Level : Critical (CVSS 9.3) ❌ → Mitigated ✔️

If Patching Delayed

1. Primary Workaround: Disable chroot functionality via Defaults !use_chroot in sudoers
2. Filesystem Hardening: Remount /tmp and /var/tmp with nosuid,nodev,noexec
3. Monitoring: Deploy file integrity monitoring on /tmp and enhanced audit rules

Permanent Solutions

1. Patch: Upgrade to sudo 1.9.17p1 or later immediately
2. Configuration: Remove all chroot-related directives from sudoers files
3. Architecture: Implement defense-in-depth with filesystem restrictions

Verification

Check if Vulnerable

# Version check - Critical
sudo -V | head -1
# Vulnerable: versions 1.9.14 through 1.9.17

# Test chroot availability (safe check)
sudo --help | grep -i chroot
# If "-R" option appears, system is vulnerable
# Check across distributions
dpkg -l | grep sudo        # Debian/Ubuntu
rpm -qa | grep sudo        # RHEL/CentOS/Fedora
brew list | grep sudo      # macOS Homebrew

Confirm Patch Success

# Verify patch installation
sudo -V | grep -E "1.9.17p1|1.9.18|1.10"

# Test protection - should error
sudo -R /tmp/test whoami 2>&1 | grep -q "not permitted"
echo $?  # Should return 0 if patched
# Verify normal sudo functionality
sudo whoami
# Should return: root (if authorized)

Context & Analysis

Why This Matters

CVE-2025–32463’s critical CVSS 9.3 rating accurately reflects its severity. Unlike CVE-2025–32462 which required existing sudo access, this vulnerability can be exploited by any local user without privileges. The combination of:

• No authentication requirements
• Public proof-of-concept availability
• Universal sudo deployment
• Easy exploitation

…makes this a priority-zero patching scenario for all organizations.

Related Vulnerabilities

• CVE-2025–32462 : Companion sudo host bypass vulnerability (CVSS 2.8) — disclosed simultaneously
• CVE-2021–3156 (Baron Samedit) : Previous critical sudo heap overflow (CVSS 7.8)
• CVE-2019–14287 : Sudo bypass via user ID manipulation (CVSS 7.8)

Lessons Learned

Security isolation features like chroot must establish security boundaries before privilege evaluation begins. This vulnerability demonstrates the danger of performing privileged operations within untrusted environments, regardless of how the environment was created.

Resources

Official Sources

• Sudo Security Advisory — Official vulnerability details and patch
• MITRE CVE Entry — Complete vulnerability database entry
• Red Hat Security Advisory — Enterprise guidance

Analysis & Tools

• pr0v3rbs PoC — Technical proof of concept (Credit: pr0v3rbs & Rich Mirch)
• SOC Prime Detection Rules — Multi-platform SIEM rules
• Detection Scripts — Automated scanning tools
• Ansible Patching — Automated deployment playbooks

Threat Intelligence

Exploitation Timeline

• T+0 : June 30, 2025 — Initial disclosure and patch release
• T+1 : July 1, 2025 — Public PoC published on GitHub
• T+3 : July 3, 2025 — Detection rules released by security vendors
• T+7 : July 7, 2025 — Active exploitation observed in honeypots
• T+14 : Ongoing — Mass scanning for vulnerable systems detected

Attribution

• Discovery : Rich Mirch, Stratascale Cyber Research Unit
• Public PoC : pr0v3rbs (GitHub)
• Exploitation : Confirmed active exploitation in the wild

⚠️ This analysis is provided for defensive purposes only. All testing should be conducted only on systems you own or have explicit permission to test.

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