CVE-2026-104070 in Crayons
Summary
by MITRE • 10/06/2026
The Crayons plugin for SPIP before 3.5.0 contains a missing authorization vulnerability that allows unauthenticated attackers to modify arbitrary editable object fields by omitting the secu_ anti-forgery parameter in crayons_store.php, causing the authorization dispatcher to resolve an unconditionally-true handler instead of the proper modification check. Attackers can chain this flaw to write a malicious .html skeleton file, disclose sensitive configuration files containing the site secret, and forge a signed ajax context to execute the uploaded skeleton, achieving arbitrary PHP code execution as the web-server user.
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Analysis
by VulDB Data Team • 10/06/2026
The vulnerability identified in versions of the Crayons plugin for SPIP prior to version 3.5.0 represents a critical failure in access control mechanisms within the application's administrative interface. This flaw is classified under CWE-284, which denotes Improper Access Control, and specifically manifests as an unauthenticated modification capability that bypasses standard security checks. The root cause lies in the file crayons_store.php, where the authorization dispatcher fails to enforce mandatory anti-forgery protections. Specifically, the system relies on a parameter named secu_ to validate requests, but this validation is not strictly enforced for all entry points within the plugin's logic. When an attacker omits this security token during a request, the internal handler resolution mechanism defaults to an unconditional true state rather than performing the intended authorization check against the user session or permissions database. This design flaw effectively neutralizes the protective barrier that should prevent unauthorized users from interacting with administrative functions.
The operational impact of this vulnerability is severe due to its potential for privilege escalation and remote code execution. Because the vulnerability allows unauthenticated actors to modify arbitrary editable object fields, attackers can manipulate core configuration data stored within the SPIP database. A primary vector exploited in conjunction with this flaw involves writing a malicious .html skeleton file into the server's web-accessible directory structure. By leveraging the ability to alter these objects without authentication, an attacker can inject custom code that is subsequently rendered by the application framework. This capability transforms a simple configuration tampering issue into a full remote code execution scenario. The attacker does not need valid credentials or prior access; they only need network connectivity to the target web server and knowledge of the plugin's internal file paths and database schema structures.
The attack chain typically proceeds through several stages that compound the initial authorization bypass. First, the unauthenticated modification allows the insertion of a crafted HTML skeleton containing embedded PHP code. Second, this action often facilitates the disclosure of sensitive configuration files that contain cryptographic secrets or site-specific keys required for further exploitation steps. With access to these secrets, an attacker can forge signed AJAX contexts that appear legitimate to the application's backend processes. This forged context allows the uploaded malicious skeleton file to be executed by the web server process itself. Consequently, the attacker achieves arbitrary PHP code execution with the same privileges as the web-server user, which often includes read and write access to the entire website directory structure and potentially broader system resources depending on the hosting environment's security posture.
From a threat intelligence perspective, this vulnerability aligns with MITRE ATT&CK techniques related to Initial Access and Execution. The ability to upload and execute files corresponds to T1505.003 (Web Shell: Web Framework), while the initial bypass of access controls maps to T1078 (Valid Accounts) or more accurately in this unauthenticated context, it reflects a failure in authentication mechanisms that allows unauthorized entry similar to T1190 (Exploit Public-Facing Application). The disclosure of configuration files also relates to T1530 (Data from Local System), as the attacker extracts sensitive data necessary for maintaining persistence and escalating privileges. Understanding these mappings helps security teams prioritize remediation efforts based on known adversary behaviors associated with web application exploitation campaigns targeting content management systems like SPIP.
Mitigation strategies must focus immediately on updating the Crayons plugin to version 3.5.0 or later, where this authorization dispatcher logic has been corrected to strictly enforce the presence and validity of the secu_ anti-forgery parameter for all administrative operations. Until an update is applied, administrators should consider restricting access to the SPIP installation via IP whitelisting if possible, although this is not a robust long-term solution given that many web servers are exposed to the public internet. Additionally, implementing Web Application Firewalls with rulesets designed to detect and block requests missing standard anti-CSRF tokens can provide a temporary layer of defense against exploitation attempts. It is also critical to audit server permissions to ensure that the web-server user has minimal necessary privileges, thereby limiting the potential damage if an attacker successfully executes arbitrary code through this vulnerability. Regular monitoring for unusual file creation events in skeleton directories and anomalous AJAX request patterns can aid in early detection of such attacks in real-time environments.