CVE-2026-44957: Revive Adserver Auth Bypass Vulnerability

CVE-2026-44957 Overview

CVE-2026-44957 is a broken access control vulnerability in Revive Adserver versions 6.0.6 and earlier. The XML-RPC API exposes multiple modify methods that fail to validate access to parent entities. Authenticated users can reassign entities to parent entities they do not own, producing inconsistent ownership relationships across the ad server. The flaw maps to CWE-284: Improper Access Control and requires low privileges to exploit over the network.

Critical Impact
An authenticated low-privileged user can reparent entities through unprotected XML-RPC modify calls, corrupting ownership integrity when chained with CVE-2026-34917 or third-party API extensions that expose API functionality to low-privileged accounts.

Affected Products

Revive Adserver 6.0.6 and earlier
Revive Adserver XML-RPC API endpoints exposing modify methods
Third-party Revive Adserver API extensions that expose API functionality to low-privileged users

Discovery Timeline

2026-06-23 - CVE-2026-44957 published to NVD
2026-06-23 - Last updated in NVD database

Technical Details for CVE-2026-44957

Vulnerability Analysis

The vulnerability resides in the XML-RPC API surface of Revive Adserver 6. Several modify methods accept parameters that reference parent entities such as advertisers, campaigns, or zones. The API performs authentication but omits an authorization check against the target parent entity. An authenticated user can therefore submit a modify request that reassigns a child entity to a parent entity owned by a different account.

The result is corrupted ownership relationships within the ad server. Entities can end up under parents that the original owner does not control, breaking the integrity assumptions used for billing, reporting, and campaign delivery. Confidentiality and availability are not directly impacted, which aligns with the limited integrity-only impact reflected in the CVSS metrics.

The issue is not directly exploitable in a default deployment. The advisory states it becomes exploitable only when combined with CVE-2026-34917 or with third-party API extensions that broaden API access to low-privileged users.

Root Cause

The root cause is a missing access control check [CWE-284] inside the XML-RPC API modify handlers. The handlers validated the caller's identity but did not verify that the caller had rights over the parent entity supplied in the request. The fix adds explicit access control checks that validate access to parent entities before any modification is applied.

Attack Vector

The attack vector is network-based and requires a valid low-privileged account or a third-party extension that exposes API methods to such users. An attacker authenticates to the XML-RPC endpoint and invokes a vulnerable modify method with a parent_id value referencing an entity the attacker does not own. The server processes the change without verifying parent ownership, completing the unauthorized reparenting. Chaining with CVE-2026-34917 expands the set of accounts that can reach the vulnerable methods.

No verified proof-of-concept code is publicly available. See the HackerOne Report #3677576 for the disclosure details.

Detection Methods for CVE-2026-44957

Indicators of Compromise

XML-RPC requests to Revive Adserver invoking modify methods that include parent_id or analogous parent reference fields from low-privileged accounts.
Audit log entries showing entities reassigned to parents owned by different accounts without an administrative action preceding the change.
Sudden changes in advertiser, campaign, or zone ownership reported by tenants whose accounts were not used to make the change.

Detection Strategies

Enable verbose logging on the XML-RPC endpoint and correlate caller account, target entity, and parent entity for each modify call.
Alert on modify operations where the resulting parent entity is owned by a different account than the caller.
Review web server access logs for repeated XML-RPC POST requests from accounts that historically use only the web UI.

Monitoring Recommendations

Forward Revive Adserver application and web server logs to a centralized analytics platform for retention and correlation.
Baseline normal XML-RPC API usage per account and alert on deviations involving ownership-changing methods.
Periodically reconcile parent-child entity relationships against an authoritative ownership record to detect drift.

How to Mitigate CVE-2026-44957

Immediate Actions Required

Upgrade Revive Adserver to a version newer than 6.0.6 that includes the added access control checks on API modify methods.
Inventory any third-party API extensions and confirm whether they expose XML-RPC functionality to low-privileged users.
Rotate API credentials for any account that may have been used to test or exploit the issue.

Patch Information

The vendor has added access control checks that validate access to parent entities inside the API modify methods. Apply the fixed Revive Adserver release referenced in the HackerOne Report #3677576. Verify the deployed version after upgrade and confirm that custom plugins remain compatible with the new authorization checks.

Workarounds

Restrict network access to the XML-RPC endpoint to trusted management hosts using firewall or reverse proxy rules.
Disable the XML-RPC API entirely if it is not required for production integrations.
Remove or sandbox third-party API extensions that broaden API access to non-administrative users until the patch is applied.
Limit API account permissions to the minimum scope needed for required integrations.

bash

# Example: block XML-RPC API access at the reverse proxy except from trusted hosts
location /www/api/v2/xmlrpc/ {
    allow 10.0.0.0/24;        # trusted management subnet
    deny all;
    proxy_pass http://revive_backend;
}