Description Preview
CVE-2023-34253 affects Grav CMS versions prior to 1.7.42. The vulnerability stems from an insufficient denylist implementation that was meant to prevent dangerous functions from being executed via template injection. The protection mechanism could be bypassed in multiple ways: by using unsafe functions not included in the denylist, by using capitalized callable names, or by using fully-qualified names for function references. This allows attackers with login access to the Grav Admin panel and page creation/update permissions to inject malicious templates and achieve remote code execution on the server.
Overview
Grav is a popular flat-file content management system that doesn't require a database. The vulnerability exists in the template processing functionality where the system attempts to filter dangerous PHP functions that could be called from templates. The filtering mechanism implemented in commit 9d6a2d was insufficient and could be bypassed through multiple techniques. This is classified as CWE-94 (Code Injection), allowing attackers with administrative access to inject code that gets executed on the server. The vulnerability is particularly dangerous as it provides a path to complete system compromise through remote code execution.
Remediation
To remediate this vulnerability:
- Update Grav CMS to version 1.7.42 or later, which contains an improved denylist implementation.
- If immediate updating is not possible, restrict access to the Grav Admin panel to only trusted users.
- Monitor system logs for suspicious activity related to template modifications.
- Consider implementing additional security layers such as Web Application Firewalls that can help detect and block code injection attempts.
- Follow the principle of least privilege for all administrative accounts with access to the CMS.
References
- GitHub Advisory: https://github.com/getgrav/grav/security/advisories/GHSA-j3v8-v77f-fvgm
- Huntr.dev Vulnerability Report: https://huntr.dev/bounties/3ef640e6-9e25-4ecb-8ec1-64311d63fe66/
- Fix Commit: https://github.com/getgrav/grav/commit/71bbed12f950de8335006d7f91112263d8504f1b
- Original Vulnerable Code: https://github.com/getgrav/grav/blob/1.7.40/system/src/Grav/Common/Utils.php#L1952-L2190
- Initial Insufficient Fix Commit: https://www.github.com/getgrav/grav/commit/9d6a2dba09fd4e56f5cdfb9a399caea355bfeb83
Industry ExposureMost to leastThis section illustrates the prevalence of a specific Common Vulnerabilities and Exposures (CVE) across various industries based on customer reports. The ranking displays industries from the most to least affected by this particular vulnerability, offering valuable insight into where this CVE has been most frequently observed. This information can help organizations within these sectors prioritize their security efforts, understand their relative risk exposure compared to their peers, and focus remediation strategies where they are most needed. By understanding the industry-specific impact, organizations can make more informed decisions regarding patching, resource allocation, and overall risk management related to this CVE.
This section illustrates the prevalence of a specific Common Vulnerabilities and Exposures (CVE) across various industries based on customer reports. The ranking displays industries from the most to least affected by this particular vulnerability, offering valuable insight into where this CVE has been most frequently observed. This information can help organizations within these sectors prioritize their security efforts, understand their relative risk exposure compared to their peers, and focus remediation strategies where they are most needed. By understanding the industry-specific impact, organizations can make more informed decisions regarding patching, resource allocation, and overall risk management related to this CVE.
- Accommodation & Food ServicesAccommodation & Food Services
- Administrative, Support, Waste Management & Remediation ServicesAdministrative, Support, Waste Management & Remediation Services
- Agriculture, Forestry Fishing & HuntingAgriculture, Forestry Fishing & Hunting
- Arts, Entertainment & RecreationArts, Entertainment & Recreation
- ConstructionConstruction
- Educational ServicesEducational Services
- Finance and InsuranceFinance and Insurance
- Health Care & Social AssistanceHealth Care & Social Assistance
- InformationInformation
- Management of Companies & EnterprisesManagement of Companies & Enterprises
- ManufacturingManufacturing
- MiningMining
- Other Services (except Public Administration)Other Services (except Public Administration)
- Professional, Scientific, & Technical ServicesProfessional, Scientific, & Technical Services
- Public AdministrationPublic Administration
- Real Estate Rental & LeasingReal Estate Rental & Leasing
- Retail TradeRetail Trade
- Transportation & WarehousingTransportation & Warehousing
- UtilitiesUtilities
- Wholesale TradeWholesale Trade
