CVE-2026-48911: Apache Answer Auth Bypass Vulnerability

CVE-2026-48911 Overview

CVE-2026-48911 is a missing authorization vulnerability [CWE-306] affecting Apache Answer through version 2.0.1. The flaw resides in the external-login email binding flow, which fails to verify the authenticity of binding requests. Unauthenticated attackers can hijack arbitrary user accounts by tricking victims into clicking a crafted confirmation link. Apache has released version 2.0.2 to remediate the issue.

Critical Impact
Successful exploitation enables full account takeover of any Apache Answer user, granting attackers access to victim data, posts, and administrative privileges tied to the compromised account.

Affected Products

Apache Answer versions through 2.0.1
Apache Answer external-login email binding component
Deployments exposing account confirmation endpoints to untrusted users

Discovery Timeline

2026-08-05 - CVE CVE-2026-48911 published to NVD
2026-08-05 - Last updated in NVD database

Technical Details for CVE-2026-48911

Vulnerability Analysis

Apache Answer is an open-source question-and-answer platform that supports external identity providers for user login. The vulnerability affects the workflow that binds an external login identity to an Apache Answer account through an email confirmation step. The application processes binding confirmations without validating that the request originated from the legitimate account owner. As a result, an attacker who initiates the binding flow can produce a confirmation link that, when clicked by a victim, associates the attacker's external identity with the victim's account.

Once the binding completes, the attacker authenticates through the linked external identity provider and gains full access to the victim's Apache Answer account. The vulnerability is categorized as Insufficient Verification of Data Authenticity and maps to Missing Authentication for a Critical Function [CWE-306].

Root Cause

The root cause is the absence of an authorization check in the external-login email binding flow. The endpoint that finalizes the binding does not verify that the currently authenticated session, the binding token, and the target account belong to the same principal. This allows an attacker to craft a confirmation URL that, when visited by a victim, binds the attacker-controlled external identity to the victim's account.

Attack Vector

The attack proceeds over the network and requires user interaction. An attacker registers or initiates an external-login binding referencing a target user's email or account. The application generates a confirmation link. The attacker delivers the crafted link to the victim through phishing, forum messages, or embedded content. When the victim clicks the link while authenticated, the server completes the binding without verifying intent. The attacker then logs in through the external identity provider and takes over the victim account. See the Apache Mailing List Discussion and Openwall OSS Security Update for advisory details.

Detection Methods for CVE-2026-48911

Indicators of Compromise

Unexpected external-login bindings appearing on user accounts, particularly bindings created shortly after a user clicked an inbound link.
Successful logins from external identity providers immediately following a new binding event on the same account.
Password reset requests, email changes, or session token invalidations following unexplained external-login binding activity.

Detection Strategies

Audit Apache Answer application logs for external-login binding confirmation requests and correlate them with the originating session's authenticated user identifier.
Flag binding events where the confirmation request's session user does not match the account being bound.
Monitor referrer headers and inbound traffic to binding confirmation endpoints for links delivered from external domains or messaging platforms.

Monitoring Recommendations

Enable verbose logging on authentication and identity-binding endpoints and forward events to a centralized SIEM for correlation.
Alert on rapid sequences of binding, login, and profile-change events on the same account within short time windows.
Track user reports of unauthorized account access and cross-reference against binding activity in the preceding 24 hours.

How to Mitigate CVE-2026-48911

Immediate Actions Required

Upgrade Apache Answer to version 2.0.2 or later, which contains the authorization fix for the external-login binding flow.
Review all recent external-login binding events and revoke bindings that cannot be attributed to the legitimate account owner.
Force session invalidation and require password resets for any user accounts with suspicious binding activity.

Patch Information

Apache has released Apache Answer version 2.0.2 which adds the missing authorization check to the external-login email binding flow. Administrators should apply the update as documented in the Apache Mailing List Discussion.

Workarounds

If immediate upgrade is not possible, disable external-login providers in the Apache Answer configuration until the patched version is deployed.
Restrict access to the Apache Answer instance to trusted networks to limit exposure of the binding endpoint.
Communicate to users that they should not click account-related confirmation links received from untrusted sources until patching is complete.

bash

# Upgrade Apache Answer to the patched release
docker pull apache/answer:2.0.2
docker stop answer && docker rm answer
docker run -d -p 9080:80 -v answer-data:/data --name answer apache/answer:2.0.2