CVE-2023-49933: SchedMD Slurm Auth Bypass Vulnerability

CVE-2023-49933 Overview

CVE-2023-49933 is an Improper Enforcement of Message Integrity During Transmission vulnerability discovered in SchedMD Slurm, a widely-used open-source workload manager for high-performance computing (HPC) clusters. This flaw allows attackers to modify Remote Procedure Call (RPC) traffic in a way that bypasses message hash checks, potentially compromising the integrity of communications between Slurm components.

Critical Impact

Attackers can intercept and modify RPC communications between Slurm cluster components, bypassing integrity checks and potentially manipulating job scheduling, resource allocation, or cluster management operations.

Affected Products

• SchedMD Slurm 22.05.x (prior to 22.05.11)
• SchedMD Slurm 23.02.x (prior to 23.02.7)
• SchedMD Slurm 23.11.x (prior to 23.11.1)

Discovery Timeline

• 2023-12-14 - CVE-2023-49933 published to NVD
• 2025-11-04 - Last updated in NVD database

Technical Details for CVE-2023-49933

Vulnerability Analysis

This vulnerability falls under CWE-924 (Improper Enforcement of Message Integrity During Transmission in a Communication Channel). The flaw exists in how Slurm validates the integrity of RPC messages transmitted between cluster components such as the controller daemon (slurmctld), compute node daemons (slurmd), and client utilities.

The vulnerability allows network-positioned attackers to intercept and modify RPC traffic without the modifications being detected by Slurm's message hash validation mechanisms. This is particularly concerning in HPC environments where Slurm manages sensitive computational workloads, resource allocations, and user job submissions across potentially large cluster deployments.

The attack can be conducted remotely over the network without requiring any authentication or user interaction, making it accessible to any attacker with network visibility to Slurm's communication channels.

Root Cause

The root cause lies in improper enforcement of message integrity validation within Slurm's RPC communication protocol. The hash check mechanism that should ensure message authenticity and integrity can be bypassed, allowing modified messages to be accepted as legitimate by receiving Slurm components.

This implementation flaw means that cryptographic protections intended to detect tampering are not being properly applied or verified, creating a window for man-in-the-middle style attacks on inter-component communications.

Attack Vector

The attack vector is network-based, requiring the attacker to have a position on the network path between Slurm components. An attacker can:

1. Intercept RPC communications between Slurm daemons (e.g., between slurmctld and slurmd)
2. Modify the message payload while crafting data that bypasses hash integrity checks
3. Forward the modified message to the destination component
4. The receiving component accepts the tampered message as valid

This could enable attackers to manipulate job scheduling decisions, alter resource allocations, inject malicious commands, or disrupt cluster operations. In HPC environments running sensitive research or production workloads, such tampering could have significant consequences.

Detection Methods for CVE-2023-49933

Indicators of Compromise

• Unexpected changes in job scheduling or resource allocation behavior
• Unusual RPC traffic patterns or message sizes between Slurm components
• Discrepancies between submitted job parameters and executed job configurations
• Log entries indicating communication anomalies between slurmctld and slurmd daemons

Detection Strategies

• Monitor network traffic between Slurm components for signs of interception or modification
• Implement network intrusion detection rules to identify anomalous RPC message patterns
• Compare Slurm component logs across the cluster for inconsistencies in recorded operations
• Deploy network segmentation monitoring to detect unauthorized access to Slurm communication channels

Monitoring Recommendations

• Enable verbose logging on slurmctld and slurmd daemons to capture detailed communication records
• Implement network traffic analysis on ports used by Slurm (default 6817-6819)
• Monitor for unauthorized network access attempts to cluster management networks
• Establish baseline communication patterns for Slurm RPC traffic to identify deviations

How to Mitigate CVE-2023-49933

Immediate Actions Required

• Upgrade SchedMD Slurm to patched versions: 22.05.11, 23.02.7, or 23.11.1
• Audit network access controls to limit exposure of Slurm communication channels
• Review recent job submissions and cluster operations for signs of tampering
• Consider enabling additional authentication mechanisms if available in your Slurm configuration

Patch Information

SchedMD has released security patches addressing this vulnerability. The fixed versions are:

• Slurm 22.05.11 for the 22.05.x branch
• Slurm 23.02.7 for the 23.02.x branch
• Slurm 23.11.1 for the 23.11.x branch

For detailed patch information and download links, refer to the SchedMD Security Archive and the Slurm Announcement Archive. Fedora users should also review the Fedora Security Announcements for distribution-specific updates.

Workarounds

• Isolate Slurm cluster communications on a dedicated, secured network segment
• Implement strict firewall rules limiting access to Slurm ports from authorized systems only
• Use VPN or encrypted tunnels for Slurm communications if upgrading is not immediately possible
• Enable Slurm's authentication plugins (e.g., auth/munge) with properly secured key distribution

# Example: Verify current Slurm version and check for updates
sinfo --version

# Example: Restrict network access to Slurm ports (adjust as needed)
iptables -A INPUT -p tcp --dport 6817:6819 -s <trusted_network> -j ACCEPT
iptables -A INPUT -p tcp --dport 6817:6819 -j DROP