CVE-2026-77353: Wallos: iCalendar Injection via CRLF in Subscription Name/Notes Export
Wallos is an open-source, self-hostable personal subscription tracker. Prior to version 5.0.0, Wallos allows authenticated users to inject arbitrary iCalendar properties and events into their exported .ics feed by embedding raw CRLF sequences in subscription names or notes. Because the input validation layer only encodes HTML metacharacters but never strips newlines, and the export layer decodes those entities back before writing iCal output, an attacker with any valid account can craft a subscription whose name breaks out of the current VEVENT block and inserts fully attacker-controlled calendar events — including spoofed organizers, arbitrary email addresses in ATTENDEE properties, and misleading event content — into any calendar application subscribed to that feed. This issue has been patched in version 5.0.0.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Wallosto a version that resolves this vulnerability.Fixed in 5.0.0
Event History
Frequently Asked Questions
Who can exploit this issue?
An attacker needs any valid Wallos account and must be able to create or modify a subscription name or notes field. Exploitation also relies on someone subscribing a calendar application to the affected exported .ics feed.
What is the impact on calendar subscribers?
A malicious subscription name or note can inject arbitrary iCalendar properties and additional events into the exported feed. This can present subscribers with misleading events, spoofed organizers, and attacker-chosen ATTENDEE email addresses.
Are deployments running the default behavior affected?
The vulnerable behavior is in the handling of subscription names and notes during .ics export: newline characters are not stripped before the export layer writes iCalendar output. Any pre-5.0.0 deployment that exposes exported feeds and permits authenticated users to control those fields is affected.
What should teams do if they cannot upgrade immediately?
Restrict access to Wallos accounts and avoid sharing or subscribing to .ics feeds generated from untrusted user-controlled subscriptions. Review subscription names and notes for raw CRLF/newline characters and remove suspicious entries before distributing feeds.
How can an administrator identify possible exploitation?
Inspect subscription names and notes for embedded newline characters or iCalendar fragments such as additional VEVENT blocks, ORGANIZER properties, or ATTENDEE properties. Also inspect exported .ics feeds for unexpected events or properties not associated with legitimate subscriptions.