CVE-2025-53632: Chall-Manager Path Traversal Vulnerability

CVE-2025-53632 Overview

CVE-2025-53632 is a Path Traversal vulnerability (CWE-22) affecting Chall-Manager, a platform-agnostic system designed to start Challenges on Demand for players. The vulnerability exists in the scenario decoding functionality, where the path of files extracted from zip archives is not properly validated, leading to a classic "zip slip" attack vector.

When processing scenarios (zip archives), the application fails to sanitize file paths within the archive, allowing attackers to craft malicious archives with traversal sequences (e.g., ../) that write files outside the intended extraction directory. This can lead to arbitrary file writes on the target system.

Critical Impact

Unauthenticated attackers can exploit this vulnerability to write arbitrary files to the system, potentially leading to remote code execution through configuration file overwrites, web shell deployment, or other file-based attacks.

Affected Products

• ctfer-io chall-manager versions prior to v0.1.4
• Chall-Manager deployments processing untrusted scenario zip archives
• Any infrastructure where Chall-Manager is exposed to untrusted users

Discovery Timeline

• 2025-07-10 - CVE-2025-53632 published to NVD
• 2025-08-14 - Last updated in NVD database

Technical Details for CVE-2025-53632

Vulnerability Analysis

This vulnerability is a classic zip slip attack, a well-known class of path traversal vulnerabilities that occurs when archive extraction code fails to properly validate file paths within compressed archives. In the case of Chall-Manager, the scenario processing functionality accepts zip archives and extracts their contents without verifying that the destination paths remain within the intended extraction directory.

The attack does not require authentication or authorization, meaning any user who can submit a scenario archive to the system can potentially exploit this vulnerability. However, the vendor notes that Chall-Manager should ideally be deployed deep within infrastructure where direct user access is limited, which provides some defense-in-depth mitigation.

The potential impact includes integrity and availability compromise through arbitrary file writes. Attackers could overwrite critical system files, application configurations, or deploy malicious scripts that execute within the application context.

Root Cause

The root cause of this vulnerability lies in the scenario decompression logic within pkg/scenario/io.go. When extracting files from zip archives, the code did not validate or sanitize the file paths contained in the archive entries. This allowed malicious archives to include entries with path traversal sequences like ../../etc/passwd or ../../../var/www/html/shell.php, which would write files outside the intended extraction directory.

Attack Vector

The attack is network-accessible and requires no user interaction or special privileges. An attacker can exploit this vulnerability by:

1. Crafting a malicious zip archive containing files with path traversal sequences in their filenames
2. Submitting this archive as a scenario to the Chall-Manager system
3. When the system processes and extracts the archive, files are written to arbitrary locations on the filesystem

The patch introduced proper path validation using strings package functionality to ensure extracted file paths remain within the intended directory.

// Security patch from pkg/scenario/io.go
// This patch adds the strings package import for path validation
 	"io"
 	"os"
 	"path/filepath"
+	"strings"
 
 	errs "github.com/ctfer-io/chall-manager/pkg/errors"
 	"github.com/pkg/errors"

Source: GitHub Commit 47d188f

Detection Methods for CVE-2025-53632

Indicators of Compromise

• Unexpected files appearing in directories outside the Chall-Manager scenario extraction path
• Log entries showing extraction of files with ../ sequences in their paths
• Modified system configuration files or web-accessible directories with unknown origins
• Presence of web shells or suspicious scripts in web-accessible directories

Detection Strategies

• Monitor file system activity for write operations outside expected Chall-Manager directories
• Implement file integrity monitoring (FIM) on critical system directories and configuration files
• Log and alert on scenario upload activities, particularly for archives containing path traversal patterns
• Deploy web application firewalls (WAF) to inspect uploaded archive contents for malicious patterns

Monitoring Recommendations

• Enable verbose logging for the Chall-Manager scenario processing functionality
• Set up alerts for any file write operations to sensitive directories like /etc, /var/www, or application configuration directories
• Monitor for newly created executable files or scripts in web-accessible locations
• Implement network-level monitoring for unusual outbound connections that may indicate successful exploitation

How to Mitigate CVE-2025-53632

Immediate Actions Required

• Upgrade Chall-Manager to version v0.1.4 or later immediately
• Review system logs for any signs of exploitation or suspicious scenario uploads
• Audit file system for unexpected files that may have been written through exploitation
• Ensure Chall-Manager is not directly exposed to untrusted users and is deployed within protected infrastructure segments

Patch Information

The vulnerability has been patched in commit 47d188f and shipped in version v0.1.4. The fix adds proper path validation using the Go strings package to ensure that extracted file paths cannot escape the intended extraction directory. Organizations should upgrade to v0.1.4 or later by following the upgrade instructions in the GitHub Release v0.1.4.

For detailed information about the vulnerability and patch, refer to the GitHub Security Advisory GHSA-3gv2-v3jx-r9fh.

Workarounds

• Restrict network access to Chall-Manager to only trusted administrative users until patching is complete
• Implement additional file system permissions to limit the directories writable by the Chall-Manager process
• Deploy Chall-Manager in a containerized environment with restricted filesystem access
• Temporarily disable scenario upload functionality if immediate patching is not possible

# Configuration example - restrict Chall-Manager process filesystem access
# Run Chall-Manager with restricted user permissions
useradd -r -s /bin/false chall-manager
chown -R chall-manager:chall-manager /opt/chall-manager/scenarios
chmod 750 /opt/chall-manager/scenarios

# Use filesystem ACLs to prevent writes outside designated directories
setfacl -R -m u:chall-manager:rwx /opt/chall-manager/scenarios
setfacl -R -d -m u:chall-manager:--- /etc /var/www