CVE-2026-25699: Apache Answer Auth Bypass Vulnerability

CVE-2026-25699 Overview

CVE-2026-25699 is an information disclosure vulnerability in Apache Answer, a Q&A platform used by communities to build knowledge bases. The flaw affects all versions through 2.0.0. Timeline-related APIs fail to enforce proper authorization checks. Authenticated users with standard privileges can retrieve deleted, private, or unapproved content along with its revision history. The vulnerability is classified under [CWE-359] Exposure of Private Personal Information to an Unauthorized Actor. Apache resolved the issue in Apache Answer 2.0.1.

Critical Impact
Any authenticated user can access deleted, private, or unapproved posts and revision history through unauthorized API calls, exposing data the platform intended to hide.

Affected Products

Apache Answer versions through 2.0.0
Self-hosted Apache Answer community deployments
Apache Answer instances exposing timeline APIs to authenticated users

Discovery Timeline

2026-06-09 - CVE-2026-25699 published to NVD
2026-06-09 - Apache project announcement published via the Apache Thread Notification
2026-06-10 - Last updated in NVD database

Technical Details for CVE-2026-25699

Vulnerability Analysis

Apache Answer exposes timeline-related endpoints that return historical activity for questions, answers, and revisions. These endpoints did not validate whether the requesting user had authorization to view the underlying content. Authentication alone was treated as sufficient for retrieval.

As a result, a regular authenticated user can query the timeline API and receive metadata and revision content for posts that should be inaccessible. Affected content includes deleted posts, posts marked private, and posts pending moderator approval. The disclosed information may include user-generated content, revision diffs, and author activity that was deliberately removed or hidden.

The issue is tracked as [CWE-359] Exposure of Private Personal Information to an Unauthorized Actor. Exploitation requires user interaction and operates across a security scope boundary, which limits direct automation but does not prevent abuse by authenticated accounts.

Root Cause

The root cause is missing authorization enforcement on timeline API handlers. The application checked only that the caller was authenticated. It did not verify whether the caller had permission to view the parent question, answer, or revision history referenced by the timeline request.

Attack Vector

An attacker registers or uses an existing account on the target Apache Answer instance. The attacker then sends crafted requests to timeline endpoints referencing the identifiers of deleted, private, or unapproved content. The server returns the timeline payload and revision history without performing access control checks on the referenced object. Refer to the Apache Thread Notification and Openwall OSS Security Update for vendor-confirmed details.

Detection Methods for CVE-2026-25699

Indicators of Compromise

Unusual volumes of requests to Apache Answer timeline API endpoints from a single authenticated user account.
Access patterns that enumerate sequential question, answer, or revision identifiers.
Authenticated requests retrieving timeline data for content identifiers that were previously deleted or unpublished.

Detection Strategies

Review Apache Answer web server access logs for repeated GET requests against timeline endpoints from non-administrator accounts.
Correlate timeline API access with moderation actions to identify reads against deleted or pending-approval content.
Establish a baseline of expected timeline API call volume per user and alert on deviations.

Monitoring Recommendations

Forward Apache Answer application and reverse-proxy logs to a centralized logging platform for retention and analysis.
Monitor authentication events alongside timeline endpoint access to attribute activity to specific accounts.
Track HTTP response sizes from timeline endpoints, since bulk enumeration produces measurable spikes.

How to Mitigate CVE-2026-25699

Immediate Actions Required

Upgrade all Apache Answer deployments to version 2.0.1 or later, which contains the authorization fix.
Audit user accounts and revoke or reset credentials for accounts showing anomalous timeline endpoint access.
Restrict registration on public-facing Apache Answer instances until the upgrade is applied.

Patch Information

Apache has released Apache Answer 2.0.1 to address CVE-2026-25699. The patch adds authorization checks to timeline-related APIs so that deleted, private, and unapproved content cannot be retrieved by unauthorized authenticated users. Upgrade instructions and release details are available through the Apache Thread Notification.

Workarounds

Place Apache Answer behind a reverse proxy and block external access to timeline API routes until the upgrade is deployed.
Limit account creation to trusted users to reduce the population able to query timeline endpoints.
Apply rate limits on timeline API paths to slow enumeration attempts against deleted or private content.

bash

# Example NGINX configuration restricting timeline API access
location ~ ^/answer/api/v1/.*/timeline {
    allow 10.0.0.0/8;
    deny all;
    limit_req zone=answer_api burst=5 nodelay;
}