CVE-2026-2861 is a medium-severity information disclosure vulnerability found in Foswiki, an open-source enterprise collaboration platform. The vulnerability affects all versions from 2.1.0 through 2.1.10 and resides in an unspecified function within the Changes/Viewfile/Oops component. This flaw allows remote attackers to manipulate the component to disclose sensitive information without requiring authentication or user interaction. The vulnerability is exploitable over the network with low attack complexity and no privileges needed, increasing the risk of unauthorized data exposure. The disclosed information could potentially include internal configuration details, user data, or other sensitive content stored or processed by Foswiki. A public exploit has been released, increasing the urgency for affected users to upgrade. The issue is resolved in Foswiki version 2.1.11, which includes a patch identified by commit hashes 31aeecb58b64 and d8ed86b10e46. No known active exploitation in the wild has been reported yet, but the availability of a public exploit raises the risk of imminent attacks. The vulnerability does not affect confidentiality, integrity, or availability beyond information disclosure, but the leaked data could facilitate further attacks or reconnaissance.

The primary impact of CVE-2026-2861 is unauthorized disclosure of sensitive information from Foswiki installations. This can lead to exposure of internal documentation, user credentials, or configuration data, which attackers could leverage for further exploitation, including privilege escalation or lateral movement within an organization. Since Foswiki is often used for internal collaboration and knowledge management, the leak of such information could compromise organizational confidentiality and competitive advantage. The ease of remote exploitation without authentication increases the risk of widespread attacks, especially in environments where Foswiki is exposed to the internet. Although no direct integrity or availability impact is reported, the information disclosure could facilitate subsequent attacks that might affect these security properties. Organizations relying on Foswiki for critical documentation or sensitive data storage are at particular risk, as attackers could gain insights into internal processes or vulnerabilities. The medium severity rating reflects the balance between the limited scope of impact (information disclosure only) and the ease of exploitation.

To mitigate CVE-2026-2861, organizations should immediately upgrade all Foswiki instances to version 2.1.11 or later, which contains the official patch for this vulnerability. If immediate upgrading is not feasible, administrators should restrict network access to Foswiki servers, limiting exposure to trusted internal networks only. Implementing web application firewalls (WAFs) with rules to detect and block suspicious requests targeting the Changes/Viewfile/Oops component can provide temporary protection. Regularly audit Foswiki logs for unusual access patterns or attempts to exploit this vulnerability. Additionally, review and minimize the amount of sensitive information stored in Foswiki to reduce potential exposure. Organizations should also ensure that Foswiki instances are not directly accessible from the public internet unless necessary and are protected by strong network segmentation and access controls. Monitoring threat intelligence feeds for any emerging exploits or attack campaigns targeting this vulnerability is recommended to respond promptly to active threats.