CVE-2026-31882: 
JavaScript vulnerability analysis and mitigation

CVE-2026-31882 is an SSE (Server-Sent Events) authentication bypass vulnerability in Dagu, an open-source workflow orchestration tool, that allows unauthenticated network attackers to access real-time DAG execution data, workflow configurations, execution logs, and queue status. When Dagu is configured with HTTP Basic authentication (DAGU_AUTH_MODE=basic), all SSE endpoints are accessible without any credentials, bypassing the authentication that protects the REST API. The vulnerability affects all versions of Dagu prior to 2.2.4. It was disclosed on March 13, 2026, with a patch released the same day. The CVSS v3.1 base score is 7.5 (High) (GitHub Advisory, Dagu Security Advisory).

The root cause is classified as CWE-306 (Missing Authentication for Critical Function). The vulnerable function buildStreamAuthOptions() in internal/service/frontend/server.go (lines 1177–1201) constructs an auth.Options struct for SSE endpoints with BasicAuthEnabled: true but omits AuthRequired, which defaults to false in Go. The authentication middleware at internal/service/frontend/auth/middleware.go (lines 181–183) then allows unauthenticated requests through when AuthRequired is false. Notably, the developers had left a FIXME comment in the code acknowledging the incomplete implementation. All SSE routes are affected, including /api/v1/events/dags, /api/v1/events/dag-runs, /api/v1/events/dag-runs/{name}/{dagRunId}/logs, /api/v1/events/queues, and related sub-endpoints. A public proof-of-concept using simple curl commands is included in the security advisory (Dagu Security Advisory, Fix PR).

Successful exploitation allows an unauthenticated attacker over the network to enumerate all workflow (DAG) names, descriptions, file paths, schedules, and tags; monitor real-time execution status; and read stdout/stderr execution logs that commonly contain sensitive data such as API keys, database credentials, authentication tokens, and internal hostnames. Attackers can also map server directory structure and deployment details from file paths and workflow configurations, and observe queue state to understand system load and pending work. The impact is limited to confidentiality — there is no integrity or availability impact — but the exposure of credentials within logs could enable lateral movement or further compromise of connected systems (GitHub Advisory, Dagu Security Advisory).

A public proof-of-concept is available in the official security advisory, consisting of concrete curl commands that demonstrate unauthenticated access to SSE endpoints without any credentials. No exploit kits or threat actor attribution have been identified, and there is no evidence of in-the-wild exploitation at this time. The EPSS score is approximately 0.17% (0.00186), placing it in the 38th percentile for exploitation probability within 30 days. The vulnerability is not listed in the CISA KEV catalog. Exploitation requires no authentication, no user interaction, and low attack complexity, making it trivially exploitable against any internet-exposed Dagu instance running in basic auth mode (Dagu Security Advisory, GitHub Advisory).

1. Reconnaissance: Identify internet-facing Dagu instances using tools like Shodan or Censys, searching for the Dagu web UI (default port 8080). Confirm the instance is running with basic auth mode by checking that the REST API returns HTTP 401 (e.g., curl -s -o /dev/null -w "%{http_code}" http://<target>:8080/api/v1/dags).
2. Confirm SSE bypass: Send an unauthenticated request to the /api/v1/events/dags SSE endpoint and verify it returns HTTP 200 with live data: curl -s -N http://<target>:8080/api/v1/events/dags
3. Enumerate workflows: Parse the SSE stream output to collect all DAG names, file paths, schedules, tags, and execution status from the returned JSON payload.
4. Extract execution logs: Using DAG names and run IDs obtained in the previous step, access execution logs without credentials: curl -s -N http://<target>:8080/api/v1/events/dag-runs/{dagName}/{runId}/logs — harvest any API keys, database credentials, tokens, or internal hostnames present in stdout/stderr output.
5. Map infrastructure: Analyze file paths and workflow configurations from the enumerated data to understand server directory structure, deployment details, and connected systems for potential lateral movement (Dagu Security Advisory).

• Network: Unauthenticated HTTP GET requests (no Authorization header) to SSE endpoints such as /api/v1/events/dags, /api/v1/events/dag-runs, /api/v1/events/queues, and /api/v1/events/dag-runs/{name}/{runId}/logs from external or unexpected IP addresses; long-lived HTTP connections (SSE streams) from unknown clients.
• Logs: Web server access logs showing HTTP 200 responses to /api/v1/events/* endpoints without an Authorization header present; repeated or sequential access to multiple SSE endpoints from the same source IP in a short timeframe.
• Process/Behavior: Unusual volume of SSE connections to the Dagu frontend service; connections from IP addresses not associated with known workflow consumers or monitoring systems (Dagu Security Advisory).

The primary remediation is to upgrade Dagu to version 2.2.4 or later, which sets AuthRequired: true for SSE endpoints in basic auth mode, enforcing credential validation consistent with REST API behavior (Dagu v2.2.4 Release, Fix Commit). As an interim workaround, implement network-level access controls (firewall rules, reverse proxy authentication) to restrict access to the Dagu API and web interface to trusted networks only. Additionally, review and sanitize workflow logs and DAG parameters to ensure sensitive data such as credentials and tokens are not exposed in execution logs, and consider using a dedicated secret management system to inject credentials at runtime rather than embedding them in workflow configurations.

The vulnerability was reported by security researcher 0xkakash1 and disclosed via the GitHub Security Advisory program on March 13, 2026. The Dagu maintainer (yohamta0) merged the fix (PR #1752) on March 10, 2026 — prior to public disclosure — and released version 2.2.4 the same day. Community reaction on GitHub was modest, with the fix PR receiving a thumbs-up reaction and the release attracting rocket emoji reactions, indicating awareness among active users. No significant mainstream media coverage or notable researcher commentary beyond the advisory itself has been identified (Dagu Security Advisory, Fix PR).