CVE-2026-23626: Kimai Information Disclosure Vulnerability

CVE-2026-23626 Overview

CVE-2026-23626 is an Information Exposure vulnerability affecting Kimai, a web-based multi-user time-tracking application. The vulnerability exists in Kimai's export functionality, which uses a Twig sandbox with an overly permissive security policy (DefaultPolicy) that allows arbitrary method calls on objects available in the template context. An authenticated user with export permissions can deploy a malicious Twig template that extracts sensitive information including environment variables, all user password hashes, serialized session tokens, and CSRF tokens.

Critical Impact

Authenticated attackers with export permissions can extract highly sensitive data including password hashes for all users, environment variables, session tokens, and CSRF tokens, potentially leading to full account compromise and system takeover.

Affected Products

• Kimai versions prior to 2.46.0
• Kimai installations with export functionality enabled
• Systems where users have been granted export permissions

Discovery Timeline

• 2026-01-18 - CVE CVE-2026-23626 published to NVD
• 2026-01-18 - Last updated in NVD database

Technical Details for CVE-2026-23626

Vulnerability Analysis

The vulnerability stems from Kimai's implementation of Twig template rendering within its export functionality. Twig is a popular PHP templating engine that includes a sandbox mode designed to safely execute untrusted template code. However, Kimai configured this sandbox with the DefaultPolicy, which fails to adequately restrict the methods that can be called on objects passed into the template context.

When an authenticated user with export permissions creates or uploads a custom export template, the Twig sandbox should prevent access to sensitive application internals. Due to the permissive security policy, attackers can craft templates that invoke arbitrary methods on objects available in the template context, effectively bypassing the sandbox protections entirely.

This vulnerability is classified under CWE-1336 (Improper Neutralization of Special Elements Used in a Template Engine), highlighting the failure to properly sanitize or restrict template engine operations.

Root Cause

The root cause is the use of Twig's DefaultPolicy for the sandbox security configuration. This default policy is not restrictive enough for untrusted user input scenarios. The policy fails to define explicit allowlists for methods and properties that can be accessed, instead relying on implicit rules that permit far more access than intended for a security-sensitive export feature.

The vulnerable implementation allows template authors to traverse object graphs and invoke getter methods, database queries, and other sensitive operations that expose internal application state.

Attack Vector

The attack requires network access and an authenticated user account with export permissions. The attacker crafts a malicious Twig template containing method calls designed to extract sensitive data. When this template is processed through the export functionality, the Twig engine executes the embedded method calls, returning sensitive information such as:

• Environment variables containing database credentials and API keys
• Password hashes for all user accounts stored in the application
• Serialized session tokens that could enable session hijacking
• CSRF tokens that could facilitate cross-site request forgery attacks

The attack is particularly dangerous because the changed scope allows information to affect resources beyond the vulnerable component, potentially compromising the entire user base.

Detection Methods for CVE-2026-23626

Indicators of Compromise

• Unusual or complex Twig templates uploaded to the export functionality
• Export operations that return abnormally large amounts of data
• Access patterns showing users repeatedly testing export features
• Log entries indicating template parsing errors or unusual object access patterns
• Unexpected access to sensitive configuration or user data endpoints

Detection Strategies

• Monitor export template contents for suspicious Twig constructs such as arbitrary method calls or object traversal patterns
• Implement logging for all export template modifications and executions
• Review audit logs for users with export permissions accessing sensitive data
• Deploy application-level monitoring to detect unusual response sizes from export operations
• Analyze Twig template syntax for patterns indicative of information disclosure attempts

Monitoring Recommendations

• Enable detailed logging for the Kimai export functionality
• Set up alerts for template modifications by users with export permissions
• Monitor for bulk data extraction patterns through export features
• Review access control configurations to ensure export permissions are granted only to trusted users
• Implement rate limiting on export operations to slow potential extraction attempts

How to Mitigate CVE-2026-23626

Immediate Actions Required

• Upgrade Kimai to version 2.46.0 or later immediately
• Review all user accounts with export permissions and remove access from untrusted users
• Audit existing export templates for potentially malicious content
• Rotate sensitive credentials that may have been exposed, including database passwords and API keys
• Reset all user passwords as a precaution if compromise is suspected

Patch Information

The vulnerability has been patched in Kimai version 2.46.0. The fix implements a more restrictive Twig sandbox security policy that properly limits method calls available to export templates.

Detailed patch information is available through the following resources:

• GitHub Commit Update
• GitHub Pull Request 5757
• GitHub Release 2.46.0
• GitHub Security Advisory GHSA-jg2j-2w24-54cg

Workarounds

• Temporarily disable the export functionality until the patch can be applied
• Revoke export permissions from all non-essential user accounts
• Implement network-level access controls to restrict who can access export features
• Deploy a web application firewall (WAF) to inspect and block suspicious template content
• Consider placing Kimai behind a VPN or authentication proxy to limit exposure

# Configuration example
# Restrict export permissions in Kimai user management
# Navigate to Admin > Users and review export permission grants
# Remove export permissions from untrusted accounts

# Verify installed Kimai version
grep -i "version" /path/to/kimai/composer.json

# Update Kimai to patched version
cd /path/to/kimai
git fetch --tags
git checkout 2.46.0
composer install --no-dev --optimize-autoloader
bin/console cache:clear