CVE-2026-12863: Venueless Unvalidated Redirect Vulnerability

CVE-2026-12863 Overview

CVE-2026-12863 is an unvalidated redirect vulnerability in Venueless, an open-source virtual event platform. The flaw resides in the application's social login functionality, where the redirect destination is not properly validated after authentication. Attackers can craft URLs that originate from the trusted Venueless domain but redirect victims to attacker-controlled sites. This abuse pattern, classified as [CWE-601] Open Redirect, enables convincing phishing campaigns that leverage the legitimacy of the Venueless domain. The vulnerability requires user interaction and low-privileged access to exploit.

Critical Impact
Attackers can leverage the trusted Venueless domain to redirect authenticated users to malicious sites, facilitating credential theft and phishing attacks against event participants.

Affected Products

Venueless virtual event platform (social login component)
See the GitHub Security Advisory GHSA-m87f-7c4r-w4p3 for specific affected versions
Deployments exposing the social login flow to network access

Discovery Timeline

2026-06-22 - CVE-2026-12863 published to NVD
2026-06-23 - Last updated in NVD database

Technical Details for CVE-2026-12863

Vulnerability Analysis

The vulnerability stems from improper validation of redirect parameters within Venueless' social login workflow. Social login flows typically accept a next or redirect parameter that determines where the user lands after authenticating through a third-party identity provider. Venueless accepts arbitrary destinations in this parameter without restricting them to an allowlist of internal paths or trusted hosts. Attackers can craft a URL pointing to the legitimate Venueless instance that, after social login completion, forwards the browser to a domain under attacker control. Because the initial URL displays the trusted Venueless hostname, victims are more likely to trust the eventual landing page.

Root Cause

The root cause is missing destination validation in the social login redirect handler, classified as [CWE-601] URL Redirection to Untrusted Site (Open Redirect). The application does not enforce that post-authentication redirects resolve to same-origin paths or to a curated allowlist of trusted hosts.

Attack Vector

An attacker constructs a phishing link using the legitimate Venueless domain with a manipulated redirect parameter pointing to an attacker-controlled site. The victim clicks the link, completes social login on the genuine Venueless instance, and is then transparently redirected to a credential-harvesting page mimicking Venueless or the identity provider. Exploitation requires user interaction and is delivered over the network. The technical specifics are documented in the GitHub Security Advisory.

Detection Methods for CVE-2026-12863

Indicators of Compromise

Web server access logs containing social login URLs with next, redirect, or similar parameters pointing to external domains
Outbound HTTP 302 responses from Venueless redirecting to non-Venueless hosts immediately following authentication callbacks
User reports of unexpected landing pages or credential prompts after logging into Venueless

Detection Strategies

Parse application logs for redirect parameters in social login endpoints and flag values resolving outside the configured Venueless domain
Correlate authentication callback events with subsequent redirect responses to identify off-domain destinations
Monitor email and chat security gateways for inbound links containing Venueless URLs with suspicious redirect parameters

Monitoring Recommendations

Enable verbose logging on the social login and OAuth callback handlers to capture all redirect targets
Track anomalous spikes in social login traffic that may indicate phishing campaign distribution
Alert on user-reported phishing attempts referencing the Venueless domain and pivot on the embedded redirect parameter

How to Mitigate CVE-2026-12863

Immediate Actions Required

Upgrade Venueless to the patched version referenced in the GitHub Security Advisory GHSA-m87f-7c4r-w4p3
Notify event organizers and participants about the phishing risk and instruct them to verify URLs before submitting credentials
Review historical access logs for evidence of exploitation against your user base

Patch Information

The Venueless maintainers have published a security advisory at GHSA-m87f-7c4r-w4p3 describing the fix. Apply the upstream patch that validates redirect targets against an allowlist of trusted destinations.

Workarounds

Restrict the social login redirect parameter at a reverse proxy or web application firewall by rejecting requests where the redirect value contains external hostnames or protocol-relative URLs
Temporarily disable social login and require local authentication until the patched version is deployed
Add Content Security Policy and referrer policy directives to reduce the effectiveness of redirect-based phishing chains

bash

# Example nginx rule blocking off-domain redirect parameters on social login endpoints
location /auth/ {
    if ($arg_next ~* "^(https?:)?//(?!venueless\.example\.com)") {
        return 400;
    }
    proxy_pass http://venueless_backend;
}