CVE-2024-10041: Linux-pam Information Disclosure Flaw

CVE-2024-10041 Overview

A speculative execution side-channel vulnerability has been discovered in Linux-PAM (Pluggable Authentication Modules), a critical authentication framework used across Linux distributions. This vulnerability allows a local attacker to exploit branch prediction mechanisms to speculatively execute Return-Oriented Programming (ROP) chains, potentially leaking sensitive authentication data including password hashes stored in /etc/shadow.

The vulnerability exists because secret information is stored in memory where an attacker can manipulate the victim program's execution by sending characters to its standard input (stdin). By training the branch predictor, an attacker can cause speculative execution of malicious code paths that expose sensitive authentication credentials.

Critical Impact

Local attackers with low privileges can potentially extract password hashes from /etc/shadow during authentication operations, enabling offline password cracking attacks.

Affected Products

• Linux-PAM (all versions)
• Red Hat Enterprise Linux 7.0
• Red Hat Enterprise Linux 8.0
• Red Hat Enterprise Linux 9.0

Discovery Timeline

• October 23, 2024 - CVE-2024-10041 published to NVD
• December 18, 2024 - Last updated in NVD database

Technical Details for CVE-2024-10041

Vulnerability Analysis

This vulnerability falls under CWE-922 (Insecure Storage of Sensitive Information) and represents a side-channel attack vector targeting the speculative execution capabilities of modern processors. The flaw affects how Linux-PAM handles sensitive authentication data in memory during the authentication process.

The attack leverages speculative execution, a CPU optimization technique where the processor predicts and pre-executes instructions before knowing if they're actually needed. By manipulating the branch predictor through carefully crafted input, an attacker can cause the CPU to speculatively execute an ROP chain that accesses protected memory regions containing password data.

The local attack vector requires the attacker to have existing low-privilege access to the target system. The high complexity rating reflects the sophisticated nature of the attack, which requires precise timing and branch predictor manipulation to successfully extract sensitive data.

Root Cause

The root cause of CVE-2024-10041 lies in the insecure handling of sensitive authentication information in memory during PAM operations. When a program performs authentication using PAM modules, password data and related secrets are temporarily stored in memory in a manner that can be accessed through speculative execution side channels.

The vulnerability is exacerbated by the predictable nature of PAM's authentication flow, which allows attackers to train the branch predictor by sending specific input patterns to the target program's stdin. This enables controlled speculative execution that can leak the contents of memory regions that would normally be inaccessible.

Attack Vector

The attack requires local access to the target system with low-level user privileges. The attacker must be able to:

1. Send input to a victim program's standard input stream
2. Train the branch predictor through repeated input patterns
3. Trigger speculative execution of an ROP chain
4. Extract leaked data through cache timing side channels

The attack targets authentication operations where sensitive password information from /etc/shadow is being processed, making it particularly dangerous during user login events, sudo operations, or other PAM-authenticated actions.

The speculative execution side-channel nature of this vulnerability means that traditional memory protection mechanisms are bypassed, as the CPU speculatively accesses protected memory before permission checks are enforced.

Detection Methods for CVE-2024-10041

Indicators of Compromise

• Unusual patterns of stdin input to PAM-authenticated processes
• Abnormal authentication timing or repeated failed authentication attempts
• Evidence of cache timing attacks (unusual cache access patterns)
• Suspicious processes interacting with authentication services during sensitive operations

Detection Strategies

• Monitor for unusual input patterns to authentication-related processes
• Implement hardware performance counter monitoring for speculative execution anomalies
• Deploy endpoint detection solutions capable of identifying side-channel attack patterns
• Audit access to /etc/shadow and authentication-related files

Monitoring Recommendations

• Enable detailed logging for PAM authentication events
• Monitor system call patterns around authentication operations
• Track process interactions with authentication services
• Implement real-time alerting for suspicious authentication timing patterns

How to Mitigate CVE-2024-10041

Immediate Actions Required

• Apply vendor-provided security patches for Linux-PAM immediately
• Review and update Red Hat Enterprise Linux systems to patched versions
• Consider enabling additional speculative execution mitigations at the kernel level
• Audit local user access and remove unnecessary accounts

Patch Information

Red Hat has released security advisories addressing this vulnerability across affected Enterprise Linux versions. System administrators should apply the following updates:

• Red Hat Security Advisory RHSA-2024:10379
• Red Hat Security Advisory RHSA-2024:11250
• Red Hat Security Advisory RHSA-2024:9941

For detailed patch information and CVE analysis, consult the Red Hat CVE Analysis for CVE-2024-10041. Additional technical details are available in Red Hat Bug Report #2319212.

Workarounds

• Restrict local user access to systems processing sensitive authentication data
• Implement strict separation between untrusted user processes and authentication services
• Enable kernel-level speculative execution mitigations where available
• Consider hardware upgrades to processors with improved speculative execution protections

# Update PAM packages on Red Hat Enterprise Linux
sudo dnf update pam

# Verify current PAM version
rpm -q pam

# Check for available security updates
sudo dnf check-update --security