CVE-2026-23944: Arcane Docker Manager Auth Bypass Flaw

CVE-2026-23944 Overview

CVE-2026-23944 is an authentication bypass vulnerability in Arcane, a Docker container management interface. Prior to version 1.13.2, the environment proxy middleware in Arcane processed /api/environments/{id}/... requests for remote environments before authentication was enforced. When the environment ID was not local, the middleware proxied the request and attached the manager-held agent token, even if the caller was unauthenticated. This enabled unauthenticated access to remote environment operations including listing containers, streaming logs, and other agent endpoints.

Critical Impact

Unauthenticated attackers can access and manipulate remote Docker environment resources via the proxy, potentially leading to data exposure, unauthorized container modifications, or complete service disruption across managed environments.

Affected Products

• Arcane Docker Management Interface versions prior to 1.13.2
• Remote environments connected to vulnerable Arcane manager instances
• Docker containers, images, networks, and volumes managed through affected deployments

Discovery Timeline

• January 19, 2026 - CVE-2026-23944 published to NVD
• January 19, 2026 - Last updated in NVD database

Technical Details for CVE-2026-23944

Vulnerability Analysis

This vulnerability is classified under CWE-306 (Missing Authentication for Critical Function). The flaw resides in the middleware layer responsible for routing requests to remote environment agents. The core issue stems from improper ordering of security controls in the request processing pipeline.

When a request targets /api/environments/{id}/... endpoints, the proxy middleware intercepts it and determines whether the target environment is local or remote. For remote environments, the middleware automatically attaches the agent authentication token stored by the manager before forwarding the request. The critical oversight is that this token attachment and proxying occurs before the middleware verifies that the original request itself came from an authenticated user.

This architectural flaw allows an unauthenticated attacker to craft requests targeting remote environment endpoints. The proxy middleware processes these requests, attaches valid agent tokens, and forwards them to remote agents—all without requiring the attacker to authenticate. The remote agent, receiving a properly authenticated request from the trusted manager, processes it without question.

Root Cause

The root cause is the improper sequencing of middleware operations in the request handling pipeline. The environment proxy middleware was registered and executed before authentication middleware in the processing chain. This architectural decision meant that requests matching remote environment patterns were proxied with valid agent tokens before any authentication check could reject unauthorized requests. The fix requires reordering middleware to ensure authentication is validated before any proxying or token attachment occurs.

Attack Vector

The vulnerability is exploitable over the network without any authentication requirements. An attacker with network access to an Arcane manager instance can send crafted HTTP requests to remote environment endpoints. The attack flow involves:

1. Attacker identifies an Arcane manager instance exposed on the network
2. Attacker enumerates or guesses valid environment IDs
3. Attacker sends unauthenticated requests to /api/environments/{id}/... endpoints
4. Proxy middleware attaches valid agent token and forwards request
5. Remote agent processes the authenticated request, returning sensitive data or executing operations

// Security patch in backend/internal/bootstrap/router_bootstrap.go
// Source: https://github.com/getarcaneapp/arcane/commit/2008e1b93b25d0c4c3fff3af07843766231614eb

 	"github.com/getarcaneapp/arcane/backend/internal/config"
 	"github.com/getarcaneapp/arcane/backend/internal/huma"
 	"github.com/getarcaneapp/arcane/backend/internal/middleware"
+	"github.com/getarcaneapp/arcane/backend/internal/utils/cookie"
 	"github.com/getarcaneapp/arcane/types"
 )
 
 var registerPlaywrightRoutes []func(apiGroup *gin.RouterGroup, services *Services)
 
-func setupRouter(cfg *config.Config, appServices *Services) *gin.Engine {
+var loggerSkipPatterns = []string{
+	"GET /api/environments/*/ws/containers/*/logs",
+	"GET /api/environments/*/ws/containers/*/stats",
+	"GET /api/environments/*/ws/containers/*/terminal",
+	"GET /api/environments/*/ws/projects/*/logs",
+	"GET /api/environments/*/ws/system/stats",
+	"GET /_app/*",
+	"GET /img",
+	"GET /api/fonts/sans",
+	"GET /api/fonts/mono",
+	"GET /api/fonts/serif",
+	"GET /api/health",
+	"HEAD /api/health",
+}
+
+func shouldLogRequest(c *gin.Context) bool {
+	mp := c.Request.Method + " " + c.Request.URL.Path
+	for _, pat := range loggerSkipPatterns {
+		if pat == mp {
+			return false

The patch adds the cookie utility import for proper authentication handling and introduces request filtering patterns, restructuring how authentication is enforced before proxy operations.

Detection Methods for CVE-2026-23944

Indicators of Compromise

• Unauthenticated HTTP requests to /api/environments/{id}/* endpoints in web server access logs
• Unusual patterns of container listing, log streaming, or management operations from unrecognized sources
• Agent tokens being used from IP addresses that don't match known manager instances
• Spike in remote environment API calls without corresponding authenticated user sessions

Detection Strategies

• Monitor web server logs for requests to environment proxy endpoints that lack valid session cookies or authentication headers
• Implement network-level monitoring to detect direct access to Arcane manager ports from untrusted sources
• Review audit logs for container operations that don't correlate with legitimate user activity
• Deploy Web Application Firewall (WAF) rules to detect and block unauthenticated requests to sensitive environment endpoints

Monitoring Recommendations

• Enable verbose logging for all requests to /api/environments/ paths and correlate with authentication events
• Set up alerts for failed authentication attempts followed by successful proxy operations
• Monitor agent communication logs on remote environments for requests originating from unexpected sources
• Implement real-time monitoring of Docker container operations across all managed environments

How to Mitigate CVE-2026-23944

Immediate Actions Required

• Upgrade Arcane to version 1.13.2 or later immediately
• Restrict network access to Arcane manager instances using firewall rules to limit exposure to trusted networks only
• Review access logs for any evidence of exploitation prior to patching
• Audit container configurations and data on all remote environments for unauthorized modifications

Patch Information

The vulnerability is patched in Arcane version 1.13.2. The fix ensures authentication checks are applied before any request proxying occurs. Technical details of the patch are available in the GitHub Pull Request #1532 and the security commit. The official release can be obtained from the Arcane v1.13.2 release page. Additional context is provided in the GitHub Security Advisory GHSA-2jv8-39rp-cqqr.

Workarounds

• Place Arcane manager instances behind a reverse proxy with authentication required for all /api/environments/ routes
• Implement network segmentation to ensure only authenticated internal services can reach the manager API
• Temporarily disable remote environment functionality until the patch can be applied
• Deploy firewall rules blocking external access to Arcane manager ports

# Example: Restrict Arcane manager access with iptables
# Allow only trusted internal network to access Arcane on port 9000
iptables -A INPUT -p tcp --dport 9000 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 9000 -j DROP

# Or use nginx as reverse proxy with authentication
# location /api/environments/ {
#     auth_request /auth;
#     proxy_pass http://localhost:9000;
# }