CVE-2026-24735: Apache Answer Flaw Exposes Deleted Content and Private User Data via Unprotected API

Overview

CVE ID: CVE-2026-24735
Affected Product: Apache Answer
Vulnerability Type: Information Disclosure / Exposure of Private Data
Affected Versions: Apache Answer versions up to and including 1.7.1
Fixed Version: 2.0.0

This vulnerability exists due to insufficient access control enforcement on a backend revision-related API. As a result, private or deleted content revisions may be disclosed to unauthorized and unauthenticated users over the network.

Severity and Risk Rating

CVSS v3.1 Score: 7.5 (High)
Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Primary Impact: Confidentiality
Integrity Impact: None
Availability Impact: None

The overall risk is considered High because sensitive data exposure may occur remotely without authentication.

Vulnerability Description

Improper authorization checks were implemented on the revision history API within Apache Answer. Historical revisions of questions or answers, including deleted or edited content, were made accessible without validating the requester’s permissions.

Even when sensitive information had been removed by users or administrators, older revisions remained retrievable through the affected API endpoint. This behavior resulted in unintended exposure of private or sensitive information such as email addresses, internal notes, or other user-submitted data.

Impact

If exploited, the following impacts may occur:

Disclosure of deleted or edited content
Exposure of personally identifiable information (PII)
Leakage of internal or confidential discussion data
Increased risk of phishing, social engineering, or privacy violations

No direct service disruption or data modification is expected; however, privacy and compliance risks are significant.

Attack Scenario

An attacker may perform the following steps:

A publicly accessible Apache Answer instance is identified.
Content identifiers are enumerated or collected from public pages.
Requests are sent to the revision/history API endpoint.
The server responds with full revision histories, including deleted content.
Exposed data is collected and analyzed offline.

No authentication, special headers, or advanced payloads are required.

Exploitability and PoC Status

Exploitability: Remote and unauthenticated
Public Exploit Code: No widely published or weaponized exploit is currently known
Proof of Concept: Conceptual exploitation is trivial and based on direct HTTP requests

Any proof-of-concept usage should be limited strictly to educational or authorized security testing purposes.

Example Proof-of-Concept Request (Educational)

curl -k -X GET https://target.example/api/content/123/revisions

If vulnerable, the response may include multiple historical versions of the content, including deleted data.

MITRE Classification

CWE-359: Exposure of Private Personal Information to an Unauthorized Actor

Detection and Monitoring

Recommended Log Sources

Web server access logs (Nginx, Apache HTTPD)
Reverse proxy or load balancer logs
Application logs from Apache Answer
Web Application Firewall (WAF) logs
API gateway logs (if applicable)

Indicators of Compromise

High volume of unauthenticated GET requests to revision or history-related endpoints
Sequential access patterns targeting multiple content IDs
Large JSON responses returned to anonymous clients
Repeated access to endpoints containing keywords such as revision, revisions, or history

Detection Rules and Queries

Splunk Query

index=web_logs http_method=GET (uri_path="*/revision*" OR uri_path="*/revisions*" OR uri_path="*/history*")
| stats count by src_ip, uri_path
| where count > 20

Elastic / KQL Query

http.request.method: "GET" and
(http.request.uri: "*revision*" or http.request.uri: "*revisions*" or http.request.uri: "*history*")

Generic SQL-Based Log Store

SELECT client_ip, request_uri, COUNT(*) AS hits
FROM access_logs
WHERE request_method = 'GET'
  AND request_uri LIKE '%revision%'
GROUP BY client_ip, request_uri
HAVING COUNT(*) > 15;

ModSecurity (WAF) Rule

SecRule REQUEST_METHOD "GET" "chain,phase:2,log,msg:'Possible CVE-2026-24735 exploitation attempt'"
SecRule REQUEST_URI "(revision|revisions|history)" "t:lowercase"

Mitigation and Remediation

Immediate Actions

Upgrade Apache Answer to version 2.0.0
Restrict unauthenticated access to revision-related endpoints
Apply rate-limiting or temporary WAF blocks if upgrade is delayed

Long-Term Actions

Review application authorization logic
Audit historical content for sensitive data exposure
Strengthen logging and anomaly detection around API usage

Official Patch and Upgrade

The vulnerability is resolved in Apache Answer 2.0.0.

Official upgrade and release details:
https://answer.apache.org/blog/answer-2.0.0-release/

Post-Remediation Validation

After upgrading:

Verify that revision endpoints return HTTP 401/403 for unauthorized users
Confirm that deleted content is no longer retrievable
Monitor logs for residual probing activity

Final Takeaway

CVE-2026-24735 represents a high-risk information disclosure issue due to missing authorization checks on a sensitive API. While exploitation is straightforward, timely patching and proper monitoring significantly reduce risk. Organizations running affected versions should prioritize upgrading and reviewing access patterns to prevent unauthorized data exposure.