CVE-2026-31937: Suricata DCERPC DOS Vulnerability

CVE-2026-31937 Overview

CVE-2026-31937 is a Denial of Service vulnerability affecting Suricata, an open-source network Intrusion Detection System (IDS), Intrusion Prevention System (IPS), and Network Security Monitoring (NSM) engine. The vulnerability stems from inefficiency in DCERPC (Distributed Computing Environment / Remote Procedure Call) buffering, which can lead to significant performance degradation when processing specially crafted network traffic.

Critical Impact

Attackers can exploit this vulnerability remotely without authentication to cause performance degradation in Suricata deployments, potentially bypassing network security monitoring and allowing malicious traffic to pass undetected during the degraded state.

Affected Products

• Suricata versions prior to 7.0.15

Discovery Timeline

• 2026-04-02 - CVE CVE-2026-31937 published to NVD
• 2026-04-02 - Last updated in NVD database

Technical Details for CVE-2026-31937

Vulnerability Analysis

This vulnerability is classified under CWE-407 (Inefficient Algorithmic Complexity), indicating that the DCERPC protocol parser in Suricata contains code paths with algorithmic inefficiencies that can be triggered by network traffic. When processing DCERPC protocol data, the buffering mechanism exhibits suboptimal performance characteristics that accumulate over time or under specific traffic patterns.

The vulnerability allows remote attackers to degrade the performance of Suricata instances by sending crafted DCERPC traffic across the network. Since no authentication or user interaction is required, any attacker with network access to monitored traffic segments can trigger this condition. The impact is limited to availability—there is no direct compromise of confidentiality or integrity of the monitored systems.

Root Cause

The root cause lies in the inefficient buffering implementation within Suricata's DCERPC protocol parser. DCERPC is commonly used in Windows environments for remote procedure calls, and Suricata must parse this traffic for threat detection purposes. The buffering mechanism responsible for handling fragmented or complex DCERPC transactions contains algorithmic inefficiencies that, when triggered, cause excessive resource consumption and performance degradation.

Attack Vector

The attack is network-based and can be executed remotely without requiring any privileges or user interaction. An attacker can craft DCERPC traffic specifically designed to trigger the inefficient buffering behavior in Suricata. As Suricata processes this traffic, the performance degradation accumulates, potentially causing the IDS/IPS to:

• Drop packets due to processing delays
• Miss malicious traffic patterns during the degraded state
• Consume excessive system resources
• Fail to keep pace with network traffic volumes

This type of attack is particularly concerning in environments where Suricata is deployed as an inline IPS, as performance degradation could result in legitimate traffic being blocked or malicious traffic being allowed through without inspection.

Detection Methods for CVE-2026-31937

Indicators of Compromise

• Abnormally high volumes of DCERPC protocol traffic from unusual sources
• Sudden spikes in Suricata process CPU or memory utilization
• Increase in Suricata packet drop rates or processing latency
• Unusual DCERPC fragmentation patterns in network traffic logs

Detection Strategies

• Monitor Suricata performance metrics including packets per second, CPU usage, and memory consumption for anomalies
• Implement alerting on sudden increases in DCERPC traffic volume or fragmentation
• Review Suricata statistics counters for DCERPC parser-related metrics
• Deploy network traffic analysis to identify unusual DCERPC communication patterns

Monitoring Recommendations

• Configure Suricata's built-in statistics logging to track parser performance over time
• Set up threshold-based alerts for resource utilization on Suricata sensors
• Monitor packet drop rates and compare against baseline performance metrics
• Implement log aggregation to correlate performance anomalies across multiple Suricata instances

How to Mitigate CVE-2026-31937

Immediate Actions Required

• Upgrade all Suricata installations to version 7.0.15 or later immediately
• Review current Suricata deployments to inventory all affected versions
• Implement resource monitoring on Suricata sensors to detect exploitation attempts
• Consider temporarily disabling DCERPC parsing if not required in your environment

Patch Information

The Open Information Security Foundation (OISF) has addressed this vulnerability in Suricata version 7.0.15. Organizations should upgrade to this version or later to remediate the vulnerability. For detailed information about the security fix, refer to the GitHub Security Advisory and the Open Information Security Issue tracker.

Workarounds

• If immediate patching is not possible, consider disabling DCERPC protocol parsing in Suricata configuration if it is not required for your security monitoring use case
• Implement rate limiting for DCERPC traffic at network boundaries to reduce potential attack surface
• Deploy additional Suricata instances to distribute load and reduce impact of performance degradation on any single sensor
• Configure Suricata's stream reassembly settings to limit buffer sizes for DCERPC traffic

# Example: Disable DCERPC application layer parsing in suricata.yaml
# Note: Only use this workaround if DCERPC inspection is not required
app-layer:
  protocols:
    dcerpc:
      enabled: no