Horizon Alert
Summary of the vulnerability and why it matters
A vulnerability has been identified in the Zephyr RTOS affecting its DNS resolver. This issue could allow a malicious DNS response to cause an out-of-bounds write, potentially leading to a denial of service or code execution.
- An error in handling DNS responses.
- Affects systems that use the Zephyr RTOS DNS resolver.
- Confirm relevance and exposure to affected systems.
Attack Path
How an attacker could exploit the issue
An attacker could send a specially crafted DNS response to a device running a vulnerable version of the Zephyr RTOS. If the device's DNS resolver is enabled, this malicious response could cause the system to write data beyond the intended buffer, potentially leading to a denial of service or code execution.
- Network access is required.
- Malicious DNS response triggers vulnerability.
- Out-of-bounds write can occur.
Live Threat
Current exploitation, exposure, and threat context
When the Zephyr RTOS DNS resolver is configured and assertions are disabled, a specially crafted DNS response could lead to an out-of-bounds write. This occurs because the `dns_unpack_name()` function incorrectly caches and reuses buffer tailroom as DNS labels are appended, potentially allowing writes beyond the allocated buffer boundaries.
- DNS query processing
- Malicious DNS response
- System instability
Operational Fix
Recommended remediation, mitigation, and detection steps
This vulnerability in the Zephyr RTOS DNS resolver could allow an unauthenticated attacker to cause an out-of-bounds write, potentially leading to a denial of service or code execution. Teams responsible for embedded systems, IoT device management, and network security should investigate. The first step is to identify all deployed instances of Zephyr with the DNS resolver enabled, assess their network exposure and criticality, and then coordinate with the device or platform owners to plan remediation.
- Identify affected devices and owners.
- Verify DNS resolver usage and network exposure.
- Plan remediation based on device criticality.
