CVE-2026-26057: Skill Scanner API Server DoS Vulnerability

CVE-2026-26057 Overview

A vulnerability exists in the API Server component of Skill Scanner, a security scanner designed to detect prompt injection, data exfiltration, and malicious code patterns in AI Agent Skills. This vulnerability could allow an unauthenticated, remote attacker to interact with the server API and either trigger a denial of service (DoS) condition or upload arbitrary files to the affected system.

Critical Impact

Unauthenticated attackers can exploit erroneous interface binding to cause memory starvation or upload files to arbitrary folders on affected devices running Skill Scanner 1.0.1 and earlier.

Affected Products

• Skill Scanner version 1.0.1 and earlier
• Systems with the API Server feature enabled (not enabled by default)

Discovery Timeline

• 2026-02-19 - CVE-2026-26057 published to NVD
• 2026-02-19 - Last updated in NVD database

Technical Details for CVE-2026-26057

Vulnerability Analysis

This vulnerability stems from improper resource exposure (CWE-668: Exposure of Resource to Wrong Sphere). The API Server in Skill Scanner erroneously binds to multiple network interfaces rather than restricting itself to the intended local or specific interface. This misconfiguration creates an unintended attack surface where unauthenticated remote attackers can send malicious API requests to the exposed server.

The exploitation path is straightforward given the network-accessible attack vector with low complexity and no authentication requirements. However, the impact is constrained to confidentiality and integrity effects without direct availability impact through the CVSS metrics, though the description indicates DoS through memory starvation is possible.

Root Cause

The root cause is an erroneous binding configuration in the API Server component. Instead of binding exclusively to localhost or a specific designated interface, the server binds to multiple interfaces, exposing the API to unintended network segments. This improper interface binding allows remote attackers to reach the API without proper network isolation.

Attack Vector

An attacker can exploit this vulnerability by sending specially crafted API requests to a device exposing the affected API Server. The attack requires no prior authentication or user interaction, making it highly accessible to remote attackers who can reach the network interface.

Two primary exploitation outcomes are possible:

1. Denial of Service via Memory Starvation: The attacker sends requests designed to consume excessive memory resources, leading to service degradation or complete unavailability.

2. Arbitrary File Upload: The attacker leverages the exposed API to upload files to arbitrary folders on the affected device, potentially enabling further compromise such as code execution or configuration tampering.

The vulnerability mechanism involves the API server accepting requests from unauthorized network sources due to the improper interface binding. Technical details regarding the specific API endpoints and request patterns can be found in the GitHub Security Advisory.

Detection Methods for CVE-2026-26057

Indicators of Compromise

• Unexpected network connections to the Skill Scanner API Server port from external or unauthorized IP addresses
• Unusual file creation in system directories or paths outside expected upload locations
• Elevated memory usage or memory exhaustion events on systems running Skill Scanner
• API request logs showing access attempts from non-localhost addresses

Detection Strategies

• Monitor network traffic for connections to the Skill Scanner API Server from unauthorized network segments
• Implement network-based intrusion detection rules to flag API requests originating from external sources
• Review system logs for file write operations in unexpected directories associated with the Skill Scanner process
• Deploy endpoint detection to identify abnormal process memory consumption patterns

Monitoring Recommendations

• Configure alerts for memory usage thresholds on hosts running Skill Scanner with API Server enabled
• Implement file integrity monitoring on critical system directories to detect unauthorized file uploads
• Enable verbose logging on the Skill Scanner API Server to capture request source addresses and payloads
• Establish baseline network behavior for Skill Scanner deployments and alert on deviations

How to Mitigate CVE-2026-26057

Immediate Actions Required

• Upgrade to Skill Scanner version 1.0.2 or later, which contains the fix for this vulnerability
• If immediate upgrade is not possible, disable the API Server feature until patching can be completed
• Implement network segmentation to restrict access to the API Server interface from untrusted networks
• Review firewall rules to block external access to ports used by the Skill Scanner API Server

Patch Information

The vulnerability has been addressed in Skill Scanner software release 1.0.2 and later versions. The fix ensures proper interface binding to prevent unauthorized remote access to the API Server. The specific code changes can be reviewed in the GitHub commit that resolves this issue.

Organizations should prioritize upgrading affected installations, particularly those where the API Server is enabled. Note that the API Server is not enabled by default, limiting exposure to systems with explicit configuration enabling this feature.

Workarounds

• Disable the API Server feature if it is not required for operational purposes
• Use host-based firewall rules to restrict API Server access to localhost only (e.g., 127.0.0.1)
• Deploy network-level access controls to limit connectivity to the API Server port from trusted hosts only
• Implement reverse proxy with authentication in front of the API Server if external access is required

# Example: Restrict API Server access using iptables
# Block external access to Skill Scanner API port (adjust port number as needed)
iptables -A INPUT -p tcp --dport <API_PORT> ! -s 127.0.0.1 -j DROP

# Allow only specific trusted IP addresses
iptables -A INPUT -p tcp --dport <API_PORT> -s 127.0.0.1 -j ACCEPT
iptables -A INPUT -p tcp --dport <API_PORT> -s <TRUSTED_IP> -j ACCEPT
iptables -A INPUT -p tcp --dport <API_PORT> -j DROP