CVE-2023-29403: Golang Go Privilege Escalation Vulnerability

CVE-2023-29403 Overview

CVE-2023-29403 is a privilege escalation vulnerability in the Go runtime on Unix platforms. The Go runtime does not behave differently when a binary is run with the setuid/setgid bits set, creating dangerous conditions that can lead to unauthorized access to sensitive data or elevated privilege execution.

This vulnerability poses significant risks in scenarios where Go binaries are executed with elevated permissions. When a setuid/setgid binary is executed with standard I/O file descriptors closed, opening any files can result in unexpected content being read or written with elevated privileges. Additionally, if a setuid/setgid program terminates via panic or signal, it may leak the contents of its CPU registers, potentially exposing sensitive information.

Critical Impact

Setuid/setgid Go binaries may leak register contents upon termination or allow file operations with elevated privileges when standard I/O descriptors are closed.

Affected Products

• Golang Go (multiple versions prior to patches)
• Fedora 38
• Other Unix-based systems running vulnerable Go versions

Discovery Timeline

• 2023-06-08 - CVE CVE-2023-29403 published to NVD
• 2025-01-06 - Last updated in NVD database

Technical Details for CVE-2023-29403

Vulnerability Analysis

The vulnerability stems from how the Go runtime handles setuid and setgid binaries on Unix platforms. Unlike many other runtimes that implement special safeguards when detecting elevated privilege execution, the Go runtime processes these binaries identically to non-privileged executions. This design oversight creates multiple attack vectors.

When a setuid/setgid binary executes with closed standard file descriptors (stdin, stdout, stderr), subsequent file open operations may inadvertently use file descriptors 0, 1, or 2. This can result in sensitive files being opened where standard I/O would normally be expected, leading to unintended data exposure or modification with elevated privileges.

Furthermore, when a setuid/setgid program terminates abnormally through a panic or signal, the Go runtime's default behavior may dump memory state including CPU register contents. In a privileged context, these registers may contain sensitive information such as cryptographic keys, authentication tokens, or other security-critical data.

Root Cause

The root cause is classified as CWE-668 (Exposure of Resource to Wrong Sphere). The Go runtime fails to implement proper security checks and mitigations when detecting that a binary is running with elevated setuid or setgid privileges. This represents a deviation from security best practices where privileged binaries should implement additional safeguards including:

• Ensuring standard file descriptors are open or explicitly closed/reopened
• Preventing memory state dumps that could leak sensitive register contents
• Restricting certain runtime behaviors that could be exploited in a privileged context

Attack Vector

The attack requires local access and user interaction. An attacker would need to:

1. Identify a Go binary installed with setuid or setgid bits on a Unix system
2. Manipulate the execution environment by closing standard I/O file descriptors before executing the binary
3. Trigger file operations within the binary that would then use the privileged file descriptors
4. Alternatively, cause the program to panic or receive a signal to potentially leak register contents

The local attack vector requires the attacker to have some level of access to the target system, but the impact can be significant as it may result in reading or writing files with elevated privileges, or disclosure of sensitive data from memory.

Detection Methods for CVE-2023-29403

Indicators of Compromise

• Unexpected file access patterns from Go binaries running with setuid/setgid permissions
• Core dumps or panic logs from privileged Go processes containing sensitive register data
• Anomalous file descriptor usage in privileged Go processes
• System logs indicating privilege escalation attempts via Go runtime behavior

Detection Strategies

• Audit all Go binaries installed with setuid or setgid bits using find / -perm /6000 -type f 2>/dev/null
• Monitor for Go process terminations that produce memory dumps in privileged contexts
• Implement file integrity monitoring on sensitive files that could be targeted through this vulnerability
• Review application logs for unexpected file access patterns from Go applications

Monitoring Recommendations

• Deploy endpoint detection and response (EDR) solutions to monitor privileged process behavior
• Configure system auditing to track setuid/setgid binary executions
• Monitor for attempts to close standard file descriptors before executing privileged binaries
• Implement alerting for core dumps from processes running with elevated privileges

How to Mitigate CVE-2023-29403

Immediate Actions Required

• Identify all Go binaries with setuid/setgid bits in your environment
• Update to patched Go versions as specified in the vendor advisory
• Consider temporarily removing setuid/setgid bits from Go binaries until patching is complete
• Review and audit any custom Go applications that may run with elevated privileges

Patch Information

Golang has released patches to address this vulnerability. The fix is documented in Go.dev CL #501223 and tracked in Go.dev Issue #60272. Additional details are available in the Go Vulnerability Database entry GO-2023-1840.

Organizations should update their Go installations to the latest patched versions. Linux distributions including Fedora have released updated packages, as noted in the Fedora Package Announcements.

Workarounds

• Remove setuid/setgid bits from Go binaries where elevated privileges are not strictly required
• Implement wrapper scripts that ensure standard file descriptors are properly initialized before executing Go binaries
• Use capability-based privilege management instead of setuid/setgid where possible
• Configure systems to suppress core dumps from privileged processes using ulimit or kernel parameters

# Remove setuid/setgid bits from Go binaries (evaluate impact first)
find /usr/local/go -perm /6000 -type f -exec chmod ug-s {} \;

# Prevent core dumps from privileged processes
echo 'fs.suid_dumpable = 0' >> /etc/sysctl.conf
sysctl -p

# Audit existing setuid/setgid Go binaries
find / -perm /6000 -type f -exec file {} \; 2>/dev/null | grep -i "go"