CVE-2025-2962 Overview
CVE-2025-2962 is a denial-of-service vulnerability in the Domain Name System (DNS) implementation of the Zephyr real-time operating system (RTOS). A crafted input triggers an infinite loop, exhausting CPU resources and rendering the affected device unresponsive. The flaw is classified under CWE-835 (Loop with Unreachable Exit Condition).
The vulnerability is remotely exploitable over the network without authentication or user interaction. Because Zephyr powers a wide range of embedded and Internet of Things (IoT) devices, the impact extends to constrained systems where availability is critical.
Critical Impact
Remote, unauthenticated attackers can force affected Zephyr devices into an infinite loop, causing sustained denial-of-service on embedded and IoT deployments.
Affected Products
- Zephyr Project Zephyr RTOS (all versions prior to the fix referenced in advisory GHSA-2qp5-c2vq-g2ww)
- Embedded and IoT devices built on the Zephyr DNS resolver stack
- Networked systems using Zephyr's DNS client implementation
Discovery Timeline
- 2025-06-24 - CVE-2025-2962 published to the National Vulnerability Database (NVD)
- 2025-10-30 - Last updated in NVD database
Technical Details for CVE-2025-2962
Vulnerability Analysis
The vulnerability resides in the Zephyr DNS implementation, which parses inbound DNS messages on behalf of client applications. A malformed or specifically crafted DNS response causes the parsing logic to enter a loop without a reachable exit condition. The affected thread consumes CPU cycles indefinitely, preventing other tasks from executing.
On an RTOS such as Zephyr, this behavior is more severe than on a general-purpose operating system. Many Zephyr deployments run on single-core microcontrollers where a stuck networking thread blocks the entire device. Watchdog timers may reset the device, but repeated triggering produces a sustained outage.
The vulnerability impacts availability only. Confidentiality and integrity are not affected, consistent with the CWE-835 classification.
Root Cause
The root cause is a missing or improperly evaluated termination condition in the DNS message parsing routine. When the parser processes a record with attacker-controlled length or pointer fields, the loop counter or pointer fails to advance toward the exit condition. The parser keeps iterating over the same data structures.
Attack Vector
An attacker delivers a crafted DNS response to a Zephyr device performing name resolution. This can occur through DNS spoofing, a malicious or compromised upstream resolver, or any network position that allows the attacker to inject DNS traffic. No authentication or user interaction is required. The technical details and proof-of-concept conditions are described in the Zephyr GitHub Security Advisory GHSA-2qp5-c2vq-g2ww.
Detection Methods for CVE-2025-2962
Indicators of Compromise
- Zephyr-based devices becoming unresponsive shortly after issuing DNS queries
- Repeated watchdog-triggered reboots correlated with outbound DNS traffic
- Anomalous DNS responses containing malformed compression pointers or oversized record fields directed at embedded endpoints
Detection Strategies
- Inspect DNS traffic to and from Zephyr devices for malformed responses, including invalid label pointers and recursive compression patterns.
- Monitor device-side telemetry for CPU saturation in the networking thread immediately following DNS resolution attempts.
- Correlate unexpected device reboots with preceding DNS exchanges to identify exploitation attempts.
Monitoring Recommendations
- Deploy network intrusion detection signatures that flag malformed DNS responses targeting embedded subnets.
- Aggregate device health metrics from IoT fleets to identify clusters of devices exhibiting simultaneous unresponsiveness.
- Log DNS resolver activity at the gateway to retain forensic evidence of malicious response payloads.
How to Mitigate CVE-2025-2962
Immediate Actions Required
- Update Zephyr to a fixed version as identified in the Zephyr Security Advisory GHSA-2qp5-c2vq-g2ww.
- Rebuild and reflash firmware for all affected devices in development, staging, and production fleets.
- Audit downstream products that integrate Zephyr to ensure vendor patches propagate to deployed devices.
Patch Information
The Zephyr Project published the fix through the GitHub Security Advisory GHSA-2qp5-c2vq-g2ww. Refer to the advisory for the specific commit, affected version ranges, and remediated releases. Integrators consuming Zephyr through a downstream Board Support Package (BSP) or vendor SDK should obtain updated firmware from the device manufacturer.
Workarounds
- Restrict DNS resolution on Zephyr devices to a trusted internal resolver and block external DNS responses at the network boundary.
- Disable DNS client functionality on devices that do not require name resolution.
- Place Zephyr-based devices on segmented networks with strict egress filtering to reduce exposure to attacker-controlled DNS traffic.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
