CVE-2026-63101: Open Event Server Auth Bypass Vulnerability

CVE-2026-63101 Overview

CVE-2026-63101 is a missing authentication vulnerability [CWE-306] in Open Event Server through version 1.19.1. The group followers CSV export endpoint lacks any authentication decorator. Unauthenticated attackers can export the complete member roster of any group, including email addresses, names, join dates, and roles. Attackers enumerate sequential group IDs, trigger an export via the unauthenticated POST endpoint, then poll the unauthenticated task status endpoint to retrieve a download URL containing the full member CSV.

Critical Impact
Remote, unauthenticated attackers can harvest complete member rosters — including personal identifiers and email addresses — from any group hosted on affected Open Event Server instances.

Affected Products

Open Event Server versions through 1.19.1
Deployments exposing the group followers CSV export endpoint
Deployments exposing the associated task status endpoint

Discovery Timeline

2026-07-17 - CVE-2026-63101 published to the National Vulnerability Database (NVD)
2026-07-17 - Last updated in NVD database

Technical Details for CVE-2026-63101

Vulnerability Analysis

The vulnerability resides in the group followers CSV export workflow of Open Event Server. The HTTP endpoint responsible for initiating a followers export accepts POST requests without validating any session, token, or role. A companion task status endpoint used to poll asynchronous job progress is similarly unauthenticated. This combination exposes the entire export pipeline to anonymous callers over the network.

An attacker enumerates numeric group identifiers through sequential brute-force. For each identifier, the attacker submits a POST request to the export endpoint, which schedules a background job. The attacker then polls the task status endpoint until the job completes and receives a download URL. Retrieving that URL returns a CSV file containing every member's email address, name, join date, and role.

Because exploitation requires only unauthenticated HTTP requests, mass extraction against exposed instances is straightforward. The disclosure is limited to confidentiality; integrity and availability of the platform are unaffected.

Root Cause

The root cause is a missing authentication decorator [CWE-306] on the group followers CSV export route and its task status route. The application relies on route-level authentication decorators to enforce access, and these two endpoints were never annotated. There is no secondary authorization check inside the handler, so the code path executes for anonymous callers.

Attack Vector

The attack is executed over the network with low complexity and no privileges. The attacker only needs the base URL of a vulnerable Open Event Server deployment. Group IDs are sequential integers, enabling exhaustive enumeration. See the VulnCheck Security Advisory and the GitHub Project Documentation for the endpoint paths and request structure.

Detection Methods for CVE-2026-63101

Indicators of Compromise

Repeated unauthenticated POST requests to the group followers CSV export endpoint with incrementing group IDs.
Bursts of unauthenticated GET requests to the task status endpoint from a single source IP.
Downloads of generated CSV artifacts by clients that never authenticated to the application.
Outbound requests to the task result download URL from IP addresses not associated with legitimate administrators.

Detection Strategies

Alert on any HTTP request to the group followers CSV export path that lacks a valid session cookie or bearer token.
Baseline normal export volume per source IP and flag statistically anomalous bursts.
Correlate export triggers with subsequent task status polling from the same client to identify automated harvesting patterns.

Monitoring Recommendations

Enable verbose access logging on the Open Event Server reverse proxy or WSGI layer.
Forward web server logs to a SIEM and build queries targeting the vulnerable route pattern.
Review authentication-free routes during code review and track their invocation counts as a security metric.

How to Mitigate CVE-2026-63101

Immediate Actions Required

Restrict network access to affected Open Event Server instances until a patched build is deployed.
Place the group followers CSV export endpoint behind an authenticated reverse proxy rule or web application firewall policy.
Audit historical access logs for prior unauthorized exports and notify affected members if data exfiltration is confirmed.

Patch Information

At the time of publication, no vendor patch reference is listed in the NVD entry for CVE-2026-63101. Monitor the upstream Open Event Server repository and the VulnCheck Security Advisory for a fixed release beyond version 1.19.1. Apply the authentication decorator to the export and task status routes once the maintainers publish a patched build.

Workarounds

Block external access to the group followers CSV export route and its task status route at the reverse proxy.
Enforce authentication at the ingress layer using rules that require a valid session cookie or API token for the affected paths.
Rate-limit anonymous requests to the application to slow sequential group ID enumeration.

bash

# Example nginx snippet blocking anonymous access to the vulnerable routes
location ~ ^/v1/groups/[0-9]+/followers/export {
    if ($http_authorization = "") { return 403; }
}
location ~ ^/v1/tasks/ {
    if ($http_authorization = "") { return 403; }
}