# CVE-2026-35599: Vikunja has an Algorithmic Complexity DoS in Repeating Task Handler

> An attacker can cause a denial of service in Vikunja by creating repeating tasks with specific intervals that trigger excessive CPU usage and database connection holds.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 10 Apr 2026
- **Updated:** 10 Apr 2026
- **Also known as:** GHSA-r4fg-73rc-hhh7, GO-2026-5608

## What is CVE-2026-35599?

CVE-2026-35599 is a medium-severity denial of service vulnerability in go-vikunja vikunja, published on 10 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Vikunja is an open-source self-hosted task management platform. Prior to 2.3.0, the addRepeatIntervalToTime function uses an O(n) loop that advances a date by the task's RepeatAfter duration until it exceeds the current time. By creating a repeating task with a 1-second interval and a due date far in the past, an attacker triggers billions of loop iterations, consuming CPU and holding a database connection for minutes per request. This vulnerability is fixed in 2.3.0.

Weakness: CWE-407 (Inefficient Algorithmic Complexity)

## Which versions are affected by CVE-2026-35599?

3 open source packages ship an affected version, including code.vikunja.io/api. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `code.vikunja.io/api` | Go | All versions | None |
| `code.vikunja.io/api` | Go | All versions | 2.3.0 |
| `code.vikunja.io/api` | Go | All versions | 2.3.0 |

Products: Vikunja Vikunja.

## How do I fix CVE-2026-35599?

Upgrade code.vikunja.io/api to 2.3.0 or later.

## Is CVE-2026-35599 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-35599 exists.

## Other vulnerabilities in go-vikunja vikunja

- [CVE-2026-28268](https://insights.sbomify.com/CVE-2026-28268/): Vikunja Vulnerable to Account Takeover via Password Reset Token Reuse (critical 9.8)
- [CVE-2026-27575](https://insights.sbomify.com/CVE-2026-27575/): Vijkunja has Weak Password Policy Combined with Persistent Sessions After Password Change (critical 9.1)
- [CVE-2026-25935](https://insights.sbomify.com/CVE-2026-25935/): Vikunja Affected by XSS Via Task Preview (high 8.6)
- [CVE-2026-35595](https://insights.sbomify.com/CVE-2026-35595/): Vikunja Affected by Privilege Escalation via Project Reparenting (high 8.3)
- [CVE-2026-33316](https://insights.sbomify.com/CVE-2026-33316/): Vikunja’s Improper Access Control Enables Bypass of Administrator-Imposed Account Disablement (high 8.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-35599 and fix it if it is affected.

What it is: CVE-2026-35599 is a medium-severity denial of service vulnerability in go-vikunja vikunja, published on 10 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-35599 exists.

Affected packages and fixed versions:
- code.vikunja.io/api (Go): affected all versions; no fix listed
- code.vikunja.io/api (Go): affected all versions; fixed in 2.3.0
- code.vikunja.io/api (Go): affected all versions; fixed in 2.3.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-35599/ (Markdown: https://insights.sbomify.com/CVE-2026-35599/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-35599
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-35599
- OSV: https://osv.dev/vulnerability/CVE-2026-35599

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-35599/
Summaries are generated and may contain mistakes; the official description above is the record.