CVE-2026-1813 in bolo-solo
Summary
by MITRE • 02/04/2026
A vulnerability was found in bolo-blog bolo-solo up to 2.6.4. Affected is an unknown function of the file src/main/java/org/b3log/solo/bolo/pic/PicUploadProcessor.java of the component FreeMarker Template Handler. The manipulation of the argument File results in unrestricted upload. It is possible to launch the attack remotely. The exploit has been made public and could be used. The project was informed of the problem early through an issue report but has not responded yet.
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Analysis
by VulDB Data Team • 03/03/2026
The vulnerability identified as CVE-2026-1813 resides within the bolo-blog bolo-solo blogging platform version 2.6.4 and earlier, specifically within the FreeMarker template handler component. This flaw manifests in the PicUploadProcessor.java file where an insecure file upload function exists that fails to properly validate or restrict file types during the upload process. The vulnerability occurs when processing File arguments through the template handler, creating an unrestricted upload condition that allows malicious actors to bypass normal security controls. The issue represents a critical security flaw that enables remote exploitation, as demonstrated by the public availability of exploit code that can be immediately utilized by threat actors. The vulnerability's presence in the FreeMarker template processing component suggests that the application's templating engine is improperly configured to handle file uploads, potentially allowing attackers to execute arbitrary code through malicious file uploads.
The technical implementation of this vulnerability stems from insufficient input validation and access control measures within the file upload handler. When users attempt to upload files through the PicUploadProcessor, the system fails to implement proper file type checking, size limitations, or content validation mechanisms that would normally prevent the upload of potentially malicious files such as web shells or executable code. This lack of sanitization creates a direct pathway for attackers to upload arbitrary files to the server, which can then be executed or accessed by unauthorized parties. The vulnerability's classification aligns with CWE-434, which describes "Unrestricted Upload of File with Dangerous Type" and represents a common pattern in web applications where file upload functionality lacks proper security controls. The attack vector is particularly concerning because it can be executed remotely without requiring authentication, making it accessible to any attacker who can reach the vulnerable system through network connections.
The operational impact of this vulnerability extends beyond simple unauthorized file uploads to potentially compromise entire server infrastructures. Attackers can leverage this flaw to deploy web shells, reverse shells, or other malicious payloads that provide persistent access to the compromised system. The unrestricted nature of the upload means that attackers can bypass typical security controls and directly execute code on the target server, potentially leading to complete system compromise, data exfiltration, and further lateral movement within network environments. The public availability of exploit code significantly increases the risk profile, as it removes the need for sophisticated attack development and allows even less technically skilled threat actors to exploit the vulnerability. Organizations running affected versions of bolo-blog bolo-solo face immediate risks of unauthorized access, data breaches, and potential regulatory compliance violations that could result in significant financial and reputational damage.
Mitigation strategies for CVE-2026-1813 require immediate action to address the root cause of the vulnerability. The most effective approach involves implementing comprehensive file validation mechanisms that restrict upload types to only trusted file formats while enforcing strict size limits and content checking procedures. Organizations should disable or remove the vulnerable file upload functionality until proper security controls are implemented, and all affected systems should be updated to patched versions of the bolo-blog bolo-solo platform. Network-level protections such as web application firewalls should be configured to monitor and block suspicious file upload patterns, while proper access controls and authentication measures should be enforced to limit who can perform file uploads. Additionally, security teams should conduct thorough audits of all file upload handlers within the application to identify and remediate similar vulnerabilities, implementing principle of least privilege access controls and regular security assessments to prevent future occurrences of this class of vulnerability that aligns with ATT&CK technique T1190 for Exploit Public-Facing Application and T1059 for Command and Scripting Interpreter.