CVE-2026-25804: Antrea Privilege Escalation Vulnerability

CVE-2026-25804 Overview

CVE-2026-25804 is an Integer Overflow vulnerability affecting Antrea, a Kubernetes networking solution designed to be Kubernetes native. The vulnerability exists in Antrea's network policy priority assignment system, where a uint16 arithmetic overflow bug causes incorrect OpenFlow priority calculations when handling large numbers of policies with various priority values. This flaw can result in potentially incorrect traffic enforcement, undermining the security posture of Kubernetes clusters relying on Antrea for network policy management.

Critical Impact

This vulnerability may allow network traffic that should be blocked by policy to pass through, or conversely, block legitimate traffic due to incorrect priority calculations in OpenFlow rules.

Affected Products

• Antrea versions prior to 2.3.2
• Antrea versions prior to 2.4.3

Discovery Timeline

• 2026-02-06 - CVE CVE-2026-25804 published to NVD
• 2026-02-09 - Last updated in NVD database

Technical Details for CVE-2026-25804

Vulnerability Analysis

The vulnerability stems from improper handling of integer arithmetic in Antrea's network policy priority system. When Kubernetes administrators deploy a large number of network policies with varying priority values, the internal calculation mechanism attempts to assign corresponding OpenFlow priorities. The use of a uint16 (16-bit unsigned integer) data type creates a boundary condition where values exceeding 65,535 wrap around to zero or small values due to integer overflow.

This arithmetic overflow directly impacts the OpenFlow rule priority ordering, which is critical for determining which network policies take precedence when multiple policies apply to the same traffic flow. The network attack vector combined with no required privileges makes this vulnerability particularly concerning for multi-tenant Kubernetes environments where network isolation is paramount.

Root Cause

The root cause is a uint16 arithmetic overflow in the network policy priority assignment logic. When calculating OpenFlow priorities from Kubernetes network policy priorities, the code does not properly validate or handle cases where the computed priority value exceeds the maximum representable value for a 16-bit unsigned integer (65,535). This boundary condition error (CWE-287) results in integer wraparound, causing high-priority policies to potentially receive lower OpenFlow priorities than intended.

Attack Vector

An attacker with the ability to create or influence Kubernetes network policies could exploit this vulnerability through network-based interactions. The attack scenario involves:

1. Creating a sufficient number of network policies to trigger the overflow condition
2. Manipulating policy priorities to cause specific OpenFlow rule ordering inversions
3. Exploiting the resulting incorrect traffic enforcement to bypass network segmentation

The vulnerability requires no authentication or user interaction to exploit, making it accessible to any entity capable of interacting with the Kubernetes API for network policy management. The impact primarily affects confidentiality and integrity through improper traffic routing, with limited availability impact.

The vulnerability manifests in the priority calculation logic within Antrea's policy controller. When policies are processed and converted to OpenFlow rules, the uint16 overflow causes incorrect priority assignments. Technical details and the specific code paths affected can be found in the GitHub Security Advisory.

Detection Methods for CVE-2026-25804

Indicators of Compromise

• Unexpected network traffic patterns that should be blocked by existing network policies
• OpenFlow rule priorities that do not match expected Kubernetes network policy priority ordering
• Log entries indicating policy synchronization issues or priority calculation anomalies
• Network connections succeeding between pods that should be isolated by policy

Detection Strategies

• Monitor Antrea controller logs for policy processing errors or unusual priority calculations
• Implement network flow monitoring to detect traffic patterns that violate expected network policies
• Audit OpenFlow rules on OVS bridges to verify priority ordering matches intended policy hierarchy
• Use Kubernetes audit logs to track network policy creation and modification events

Monitoring Recommendations

• Enable verbose logging on Antrea controller components to capture policy processing details
• Implement alerting for network policy counts approaching thresholds that could trigger overflow conditions
• Deploy network policy validation tools to compare intended vs. actual traffic enforcement
• Establish baseline network behavior profiles to detect anomalous inter-pod communications

How to Mitigate CVE-2026-25804

Immediate Actions Required

• Upgrade Antrea to version 2.4.3 or later immediately
• Audit existing network policies to identify any that may have been affected by incorrect priority enforcement
• Review network traffic logs for any suspicious communications that may have bypassed policy controls
• Limit the number of network policies with varying priorities until patching is complete

Patch Information

The Antrea maintainers have addressed this vulnerability in version 2.4.3. The fix involves proper bounds checking and handling of priority calculations to prevent uint16 overflow conditions. Organizations should upgrade to the patched version as soon as possible.

Relevant resources:

• GitHub Security Advisory
• GitHub Pull Request #7496
• Patch Commit

Workarounds

• Reduce the total number of network policies to stay below thresholds that could trigger the overflow
• Standardize network policy priorities to minimize variation and reduce overflow risk
• Implement additional network segmentation controls outside of Antrea as a defense-in-depth measure
• Consider using admission controllers to limit network policy creation until patching is complete

# Upgrade Antrea to patched version
kubectl set image deployment/antrea-controller antrea-controller=antrea/antrea-controller:v2.4.3 -n kube-system

# Verify Antrea version after upgrade
kubectl get pods -n kube-system -l app=antrea -o jsonpath='{.items[0].spec.containers[0].image}'

# Audit current network policy count
kubectl get networkpolicies --all-namespaces | wc -l