CVE-2025-1673: Zephyrproject Zephyr DOS Vulnerability

CVE-2025-1673 Overview

CVE-2025-1673 is an out-of-bounds read vulnerability in the Zephyr RTOS that can be triggered by processing a malicious or malformed DNS packet without a payload. This memory safety issue can lead to a denial of service through application crash or result in incorrect computation, potentially affecting the integrity of IoT and embedded systems running the Zephyr operating system.

Critical Impact

A network-accessible vulnerability that can crash Zephyr-based devices or cause incorrect data processing, impacting availability and integrity of embedded systems without requiring authentication.

Affected Products

• Zephyrproject Zephyr RTOS (all versions prior to patch)
• Embedded devices and IoT systems running Zephyr OS
• Network-connected Zephyr-based applications utilizing DNS functionality

Discovery Timeline

• 2025-02-25 - CVE-2025-1673 published to NVD
• 2025-02-28 - Last updated in NVD database

Technical Details for CVE-2025-1673

Vulnerability Analysis

This vulnerability is classified as CWE-125 (Out-of-Bounds Read), a memory safety issue that occurs when the DNS packet parsing logic in Zephyr attempts to read data beyond the allocated buffer boundaries. When a malformed DNS packet arrives without the expected payload, the parser fails to properly validate the packet length before attempting to access payload data.

The vulnerability can be exploited remotely over a network without requiring authentication or user interaction. An attacker can send specially crafted DNS packets to a Zephyr-based device, causing the system to read memory outside the intended buffer. This results in either a crash (denial of service) or potentially reading unintended memory contents that may lead to incorrect computation results.

The impact is primarily on system availability, as successful exploitation can crash the affected device. There is also a lower-severity integrity impact, as incorrect computations could affect application behavior. Confidentiality is not directly impacted based on the vulnerability characteristics.

Root Cause

The root cause of CVE-2025-1673 lies in insufficient input validation within the Zephyr RTOS DNS packet handling code. Specifically, the parser does not adequately verify that a DNS packet contains the expected payload data before attempting to access it. When processing a packet with missing or truncated payload, the code proceeds to read beyond the actual packet boundaries, triggering an out-of-bounds memory access.

This type of vulnerability commonly occurs in network protocol parsers where assumptions about packet structure are not verified against actual packet contents, particularly in resource-constrained embedded environments where defensive programming practices may be minimized for performance reasons.

Attack Vector

The attack vector is network-based, allowing remote exploitation without authentication. An attacker can exploit this vulnerability by:

1. Crafting a malformed DNS response or query packet with an absent or truncated payload section
2. Sending the malicious packet to a Zephyr-based device over the network
3. The device's DNS parsing code attempts to read the expected payload data
4. The out-of-bounds read occurs, causing a crash or incorrect processing

Since Zephyr RTOS is commonly deployed in IoT devices, smart sensors, and embedded systems that often operate autonomously, a successful denial of service attack could have significant operational impacts. Devices may become unresponsive until manually restarted, and in safety-critical applications, this could pose additional risks.

The vulnerability does not require any special privileges or user interaction, making it particularly dangerous for internet-facing Zephyr devices that process DNS traffic.

Detection Methods for CVE-2025-1673

Indicators of Compromise

• Unexpected crashes or reboots of Zephyr-based devices, particularly when processing network traffic
• Anomalous DNS traffic patterns containing malformed or unusually small DNS packets
• System logs showing memory access violations or segmentation faults in DNS-related code paths
• Network captures revealing DNS packets with missing or truncated payload sections

Detection Strategies

• Monitor network traffic for DNS packets with abnormal structures or missing payload sections
• Implement runtime crash analysis on Zephyr devices to identify out-of-bounds read patterns
• Deploy network intrusion detection rules to flag malformed DNS traffic targeting IoT segments
• Use SentinelOne Singularity to monitor endpoint behavior for anomalous crash patterns indicative of exploitation attempts

Monitoring Recommendations

• Enable detailed logging on network segments where Zephyr devices are deployed
• Configure alerting for device availability issues that may indicate denial of service attacks
• Monitor DNS traffic flows for unusual patterns or packet characteristics
• Implement network segmentation to limit exposure of vulnerable Zephyr devices

How to Mitigate CVE-2025-1673

Immediate Actions Required

• Review the GitHub Security Advisory GHSA-jjhx-rrh4-j8mx for specific patch details
• Update all Zephyr RTOS installations to the latest patched version
• Implement network-level filtering to block malformed DNS packets from reaching vulnerable devices
• Consider temporarily disabling DNS functionality on critical devices if not required for operation

Patch Information

The Zephyr Project has addressed this vulnerability through a security patch. Users should consult the official GitHub Security Advisory for specific version information and patch details. It is strongly recommended to update to the latest stable release of Zephyr RTOS that includes the fix for proper DNS packet payload validation.

Workarounds

• Isolate Zephyr-based devices on protected network segments with strict ingress filtering
• Deploy a DNS proxy or firewall that validates DNS packet structure before forwarding to vulnerable devices
• If DNS functionality is not required, disable it in the Zephyr configuration to eliminate the attack surface
• Implement application-level monitoring to detect and respond to device crashes promptly