CVE-2025-1713 Overview
CVE-2025-1713 is a deadlock vulnerability in the Xen hypervisor that occurs when setting up interrupt remapping for legacy PCI(-X) devices, including PCI(-X) bridges. The vulnerability arises from an unsafe lock acquisition context during the lookup of an upstream bridge, which can lead to a system deadlock and denial of service.
Critical Impact
This vulnerability enables attackers to cause a complete system deadlock, resulting in denial of service for all virtual machines and services running on affected Xen hypervisor deployments.
Affected Products
- Xen Hypervisor (versions with legacy PCI(-X) interrupt remapping support)
- Systems using PCI(-X) devices with interrupt remapping
- PCI(-X) bridges requiring upstream bridge lookups
Discovery Timeline
- 2025-07-17 - CVE CVE-2025-1713 published to NVD
- 2025-07-17 - Last updated in NVD database
Technical Details for CVE-2025-1713
Vulnerability Analysis
This vulnerability is classified as CWE-833 (Deadlock), representing a critical concurrency flaw in the Xen hypervisor's PCI interrupt remapping subsystem. The issue occurs when the hypervisor attempts to configure interrupt remapping for legacy PCI(-X) devices.
During the interrupt remapping setup process, the code must perform a lookup of the upstream bridge for legacy PCI(-X) devices and bridges. This lookup operation requires acquiring a lock. However, the context in which this lookup is performed already holds a lock that creates a circular dependency, making the lock acquisition unsafe and leading to a deadlock condition.
When the deadlock occurs, the affected Xen hypervisor becomes completely unresponsive, causing all guest virtual machines to hang and become inaccessible. This represents a significant availability impact for virtualization environments.
Root Cause
The root cause stems from improper lock ordering in the PCI interrupt remapping code path. When configuring interrupt remapping for legacy PCI(-X) devices, the code attempts to acquire a lock during the upstream bridge lookup while already holding another lock. This violates proper lock ordering principles and creates a circular wait condition—one of the four necessary conditions for deadlock (mutual exclusion, hold and wait, no preemption, and circular wait).
Attack Vector
The vulnerability can be triggered via network-based attacks without requiring any privileges or user interaction. An attacker could potentially exploit this by manipulating PCI device configurations or triggering specific interrupt remapping operations that invoke the vulnerable code path.
The attack exploits the improper synchronization in the hypervisor's PCI subsystem:
- The attacker triggers an operation requiring interrupt remapping setup for a legacy PCI(-X) device
- The hypervisor acquires an initial lock for the operation
- The upstream bridge lookup is initiated, attempting to acquire a second lock
- Due to the unsafe context, the second lock acquisition blocks indefinitely
- The deadlock condition persists, causing complete system unresponsiveness
For detailed technical information, refer to the Xen Project Security Advisory.
Detection Methods for CVE-2025-1713
Indicators of Compromise
- Xen hypervisor becoming unresponsive during PCI device initialization or configuration
- Guest virtual machines hanging simultaneously without apparent cause
- System logs showing incomplete PCI interrupt remapping operations
- Lock contention warnings or timeout messages in hypervisor logs prior to hang
Detection Strategies
- Monitor Xen hypervisor system responsiveness and implement automated health checks
- Configure watchdog timers to detect and alert on hypervisor hangs
- Implement logging for PCI interrupt remapping operations to identify suspicious patterns
- Deploy monitoring for lock acquisition timeouts in the hypervisor subsystem
Monitoring Recommendations
- Enable verbose logging for PCI subsystem operations in Xen
- Set up automated monitoring for hypervisor responsiveness with appropriate thresholds
- Configure alerting for sudden loss of connectivity to all guest VMs simultaneously
- Monitor system call latency and lock contention metrics on Xen hosts
How to Mitigate CVE-2025-1713
Immediate Actions Required
- Review the Xen Project Security Advisory for available patches
- Evaluate systems using legacy PCI(-X) devices with interrupt remapping for exposure
- Apply available security patches from your Xen distribution vendor
- Consider temporarily disabling PCI passthrough for legacy devices if patches are not immediately available
Patch Information
Security patches addressing CVE-2025-1713 are documented in XSA-467. Organizations should consult the Xen Project Security Advisory for the latest patch information. Additionally, discussions on the Openwall OSS-Security mailing list provide community insights and vendor responses.
Check with your Linux distribution or Xen package maintainer for patched versions specific to your deployment.
Workarounds
- Avoid using legacy PCI(-X) devices with interrupt remapping until patches are applied
- If possible, use PCIe devices instead of legacy PCI(-X) devices for passthrough scenarios
- Implement hypervisor redundancy to minimize impact of potential deadlocks
- Configure automated failover mechanisms for critical workloads
# Example: Check Xen version and PCI devices
# Verify current Xen version
xl info | grep xen_version
# List PCI devices to identify legacy PCI(-X) hardware
lspci -vvv | grep -E "PCI bridge|PCI-X"
# Review Xen PCI passthrough configuration
xl pci-list <domain-id>
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
