Vikunja has iCalendar Property Injection via CRLF in CalDAV Task Output

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

4.1 · CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:N/I:L/A:N

EPSS

• CVE-2026-35601: 0.20% estimated exploitation activity in the next 30 days; percentile 9.36 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The CalDAV output generator builds iCalendar VTODO entries via raw string concatenation without applying RFC 5545 TEXT value escaping. User-controlled task titles containing CRLF characters break the iCalendar property boundary, allowing injection of arbitrary iCalendar properties such as ATTACH, VALARM, or ORGANIZER. Details The ParseTodos function at pkg/caldav/caldav.go:146 concatenates the task summary directly into the iCalendar output: RFC 5545 Section 3.3.11 requires TEXT property values to escape newlines as \n, semicolons as \;, commas as \,, and backslashes as \\. None of these escaping rules are applied to Summary, Categories, UID, project name, or alarm Description fields. Go's JSON decoder preserves literal CR/LF bytes in string values, so task titles created via the REST API retain CRLF characters. When these tasks are served via CalDAV, the newlines break the SUMMARY property and the subsequent text is parsed by CalDAV clients as independent iCalendar…

Published by the source

10 Apr 2026, 15:35 UTC

Last modified by the source

10 Apr 2026, 19:45 UTC

Source last checked

26 Oct 2026, 15:19 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-2g7h-7rqr-9p4r

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-35601

Advisory: Vikunja has iCalendar Property Injection via CRLF in CalDAV Task Output
IDs: CVE-2026-35601, GHSA-2g7h-7rqr-9p4r
Record: https://patchnext.com/advisories/cve-2026-35601 (revision 1, source checked 26 Oct 2026, 15:19 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: code.vikunja.io/api 2.3.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go code.vikunja.io/api: affected <= 2.2.2; fixed in 2.3.0

## Suggested inspection (read-only)
- Go code.vikunja.io/api: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on code.vikunja.io/api.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-2g7h-7rqr-9p4r (GitHub-reviewed advisory GHSA-2g7h-7rqr-9p4r lists affected ranges: Go code.vikunja.io/api >=0 <=2.2.2)

Commands are suggestions: review each one before running it.