CVE-2026-23989: REVA Auth Bypass Vulnerability

CVE-2026-23989 Overview

CVE-2026-23989 is an authorization bypass vulnerability in the REVA interoperability platform used by OpenCloud. A flaw in the GRPC authorization middleware allows malicious users to bypass scope verification of public links. By exploiting this vulnerability through the archiver service, attackers can create archive files (zip or tar) containing all resources that the public link creator has access to, potentially leading to unauthorized data exposure.

Critical Impact

Attackers can bypass public link scope restrictions to access and exfiltrate all files accessible to the link creator, resulting in significant data breach potential.

Affected Products

• REVA versions prior to 2.42.3
• REVA versions prior to 2.40.3
• OpenCloud deployments using vulnerable REVA components

Discovery Timeline

• 2026-02-06 - CVE-2026-23989 published to NVD
• 2026-02-06 - Last updated in NVD database

Technical Details for CVE-2026-23989

Vulnerability Analysis

This vulnerability stems from improper authorization handling (CWE-863: Incorrect Authorization) in the GRPC authorization middleware of the REVA component. When a user creates a public link to share resources, the link should be scoped to only access the specific shared content. However, the flawed middleware fails to properly enforce these scope boundaries, allowing authenticated requests through the archiver service to access resources beyond the intended scope.

The attack is particularly dangerous because it leverages legitimate archiver functionality to package and exfiltrate data. An attacker with access to a public link can craft requests that bypass the scope verification, causing the archiver service to include files and directories that the original link creator has access to, but which were never intended to be shared publicly.

Root Cause

The root cause lies in insufficient path validation within the GRPC scope verification logic in internal/grpc/interceptors/auth/scope.go. The authorization middleware failed to properly validate and restrict file paths when processing requests through the archiver service, allowing path manipulation that bypasses the intended access scope of public links.

Attack Vector

The vulnerability is exploitable over the network without requiring authentication or user interaction. An attacker can:

1. Obtain access to a legitimate public link shared by a user
2. Craft malicious requests to the archiver service
3. Manipulate the request to bypass scope verification
4. Generate archive files containing resources outside the public link's intended scope
5. Download the archive containing unauthorized data

// Security patch adding path validation - Source: GitHub Commit
 import (
 	"context"
 	"fmt"
+	"path/filepath"
 	"strings"
 	"time"

Source: GitHub Commit Update

The patch introduces the path/filepath package to enable proper path validation and prevent scope bypass through path manipulation techniques.

Detection Methods for CVE-2026-23989

Indicators of Compromise

• Unusual archiver service requests accessing resources outside expected public link scopes
• High-volume archive generation requests from external IP addresses
• Archive files containing unexpected file counts or sizes relative to shared link content
• GRPC requests with manipulated path parameters targeting the archiver endpoint

Detection Strategies

• Monitor archiver service logs for requests that access paths outside the scope of the originating public link
• Implement anomaly detection for archive file sizes that exceed expected bounds for specific public links
• Track and alert on archiver requests originating from public link tokens that access parent directories or unrelated paths
• Review GRPC middleware logs for authorization scope verification failures or bypasses

Monitoring Recommendations

• Enable detailed audit logging for the REVA archiver service and GRPC middleware
• Configure alerts for archiver requests that generate archives larger than typical shared content
• Monitor for repeated archive generation attempts from single public link tokens
• Track data egress patterns from OpenCloud deployments for unusual archive download activity

How to Mitigate CVE-2026-23989

Immediate Actions Required

• Upgrade REVA to version 2.42.3 or 2.40.3 (depending on your version branch) immediately
• Review archiver service access logs for potential exploitation attempts
• Audit existing public links to identify any that may have been abused
• Consider temporarily disabling the archiver service if immediate patching is not possible

Patch Information

OpenCloud has released security patches in REVA versions 2.42.3 and 2.40.3 that address this vulnerability. The fix implements proper path validation using the path/filepath package to ensure scope verification cannot be bypassed through path manipulation. Organizations should update to these versions as soon as possible.

For detailed patch information, see the GitHub Security Advisory GHSA-9j2f-3rj3-wgpg and the security commit.

Workarounds

• Disable the archiver service temporarily if patching is not immediately feasible
• Implement network-level access controls to restrict archiver service access to trusted networks only
• Review and revoke unnecessary public links, especially those with broad access permissions
• Deploy a web application firewall (WAF) with rules to detect path traversal attempts in GRPC requests

# Configuration example
# Disable archiver service temporarily in REVA configuration
# In your reva.toml or equivalent configuration file:
[grpc.services.archiver]
enabled = false

# Alternatively, restrict archiver access via network controls
# Example iptables rule to limit archiver access to internal network
iptables -A INPUT -p tcp --dport 9142 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 9142 -j DROP