CVE-2020-14871: Oracle Solaris Privilege Escalation Flaw

CVE-2020-14871 Overview

CVE-2020-14871 is a critical buffer overflow vulnerability in the Pluggable Authentication Module (PAM) component of Oracle Solaris. This out-of-bounds write vulnerability (CWE-787) exists in the parse_user_name function within libpam, allowing unauthenticated remote attackers with network access to achieve complete system compromise. The vulnerability is easily exploitable and can be triggered through multiple protocols, including SSH, making it particularly dangerous for internet-facing Solaris systems.

Critical Impact

This vulnerability enables unauthenticated remote attackers to gain root-level access to Oracle Solaris systems. It is listed in CISA's Known Exploited Vulnerabilities Catalog and has multiple public exploits available, indicating active exploitation in the wild.

Affected Products

• Oracle Solaris 10
• Oracle Solaris 11 (versions prior to 11.1)
• Oracle Solaris 9

Discovery Timeline

• October 2020 - Oracle releases security patch via Critical Patch Update
• October 21, 2020 - CVE-2020-14871 published to NVD
• October 27, 2025 - Last updated in NVD database

Technical Details for CVE-2020-14871

Vulnerability Analysis

The vulnerability resides in the parse_user_name function within Oracle Solaris's PAM (Pluggable Authentication Module) library. This function is responsible for parsing username input during authentication processes. The root cause is an out-of-bounds write condition (CWE-787) that occurs when processing specially crafted username input.

When exploited via SunSSH, an attacker can send an oversized or malformed username string that exceeds the expected buffer boundaries. The parse_user_name function fails to properly validate the length of the input before writing it to a fixed-size buffer, resulting in a classic stack-based buffer overflow condition. This memory corruption allows attackers to overwrite critical stack data, including return addresses, enabling arbitrary code execution with root privileges.

The vulnerability is particularly severe because it can be triggered before authentication completes, meaning no valid credentials are required. While later versions of Solaris (11.1 and later) and ZFSSA (8.7 and later) have addressed this issue, legacy systems remain highly vulnerable.

Root Cause

The vulnerability stems from improper bounds checking in the parse_user_name function within the libpam library. The function allocates a fixed-size buffer for storing username data but does not adequately validate the length of incoming username strings before copying them into this buffer. This allows an attacker to supply an excessively long username that overflows the buffer boundaries, corrupting adjacent memory on the stack and enabling control flow hijacking.

Attack Vector

The attack can be executed remotely over the network through protocols that leverage PAM for authentication, most notably SSH (SunSSH). An attacker establishes a connection to the target's SSH service and supplies a maliciously crafted username during the authentication handshake. The oversized username triggers the buffer overflow in libpam's parse_user_name function, allowing the attacker to overwrite stack memory and redirect execution to attacker-controlled shellcode. Successful exploitation grants immediate root access to the compromised system.

Multiple public exploits are available targeting both Solaris 10 and Solaris 11.0 on x86 architecture, as documented in the Packet Storm security archives.

Detection Methods for CVE-2020-14871

Indicators of Compromise

• Unusual SSH connection attempts with abnormally long or malformed usernames in authentication logs
• Crash logs or core dumps from sshd or PAM-related processes
• Unexpected root-level processes spawned following SSH authentication failures
• Modifications to system files or new unauthorized user accounts created without administrative action

Detection Strategies

• Monitor SSH authentication logs (/var/adm/messages, /var/log/authlog) for connection attempts with unusually long username strings
• Deploy network intrusion detection rules to identify SSH packets containing oversized username fields
• Implement host-based intrusion detection to alert on unexpected process spawning by sshd
• Enable and review PAM debugging logs to identify authentication anomalies

Monitoring Recommendations

• Configure centralized logging for all Solaris systems to enable correlation of potential exploitation attempts
• Establish baseline metrics for SSH authentication patterns and alert on deviations
• Monitor for exploitation indicators such as unexpected outbound connections from Solaris systems following SSH activity
• Implement file integrity monitoring on critical system binaries and configuration files

How to Mitigate CVE-2020-14871

Immediate Actions Required

• Apply Oracle's October 2020 Critical Patch Update immediately to all affected Solaris 10 and 11.0 systems
• Upgrade to Solaris 11.1 or later where this vulnerability does not exist
• Restrict SSH access to trusted networks and IP addresses using firewall rules
• Consider disabling SSH temporarily on vulnerable systems until patches can be applied

Patch Information

Oracle addressed this vulnerability in the October 2020 Critical Patch Update. System administrators should consult the Oracle Security Alert - October 2020 for official patch guidance. It is important to note that Solaris 11.1 and later releases, as well as ZFSSA 8.7 and later, are not vulnerable to this issue. Organizations running Solaris 10 or Solaris 11.0 must apply the appropriate patches or upgrade to a non-vulnerable version.

Workarounds

• Implement network segmentation to isolate vulnerable Solaris systems from untrusted networks
• Use firewall rules to restrict SSH access to specific trusted IP addresses only
• Consider deploying a jump server or bastion host to mediate SSH connections to vulnerable systems
• Enable TCP Wrappers (/etc/hosts.allow, /etc/hosts.deny) to limit SSH service access

# Example: Restrict SSH access using TCP Wrappers
# Add to /etc/hosts.deny to block all SSH by default
sshd: ALL

# Add to /etc/hosts.allow to permit SSH from trusted networks only
sshd: 10.0.0.0/8, 192.168.1.0/24