Summary
Vikunja: Link-share token can enumerate users through the v2 API
Impact
Information disclosure. A link share is a low-trust credential meant to expose one project's contents; here it also exposes the membership of that project's parents and lets the holder probe for any username across the whole instance. Since share links are often forwarded or semi-public, this hands an untrusted recipient a map of internal users and a username-validation oracle useful for phishing and credential stuffing. No account is required beyond possessing a share link. Emails are not exposed.
The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions. Typical impact: unauthorized data access or execution of privileged operations.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2026-91981? CVE-2026-91981 is a medium-severity incorrect authorization vulnerability in code.vikunja.io/api (go), affecting versions <= 2.5.0. It is fixed in 2.6.0. The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions.
- Which versions of code.vikunja.io/api are affected by CVE-2026-91981? code.vikunja.io/api (go) versions <= 2.5.0 is affected.
- Is there a fix for CVE-2026-91981? Yes. CVE-2026-91981 is fixed in 2.6.0. Upgrade to this version or later.
- Is CVE-2026-91981 exploitable, and should I be worried? Whether CVE-2026-91981 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-91981 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-91981? Upgrade
code.vikunja.io/apito 2.6.0 or later.