CVE-2026-91969 in vikunja
Summary
by MITRE • 09/15/2026
vikunja versions before 2.6.0 contain a resource exhaustion vulnerability in the POST /api/v2/migration/csv/migrate endpoint that fails to limit parsed row cardinality. Authenticated attackers can upload multipart CSV files with millions of tiny records to exhaust process memory and terminate the API service.
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Analysis
by VulDB Data Team • 09/15/2026
The vulnerability identified in Vikunja versions prior to 2.6.0 represents a critical resource exhaustion flaw located within the POST /api/v2/migration/csv/migrate endpoint. This specific interface is designed to facilitate data migration by accepting CSV files, yet it lacks adequate controls on the volume of data processed during parsing. The core technical deficiency lies in the absence of limits on parsed row cardinality, meaning the application does not enforce a maximum number of records that can be ingested from an uploaded file. This architectural oversight allows for unbounded memory allocation as the system attempts to parse and store every record contained within the submitted CSV payload without restriction or early termination criteria based on size thresholds.
Authenticated attackers are able to exploit this flaw by uploading multipart CSV files containing millions of extremely small records. Although each individual record may consume minimal resources, the cumulative effect of processing a massive number of rows leads to significant memory consumption. The application's process allocates heap space for these objects in real-time during parsing, and without cardinality limits, this allocation continues until system memory is depleted. This uncontrolled resource usage directly impacts the stability of the API service, eventually causing the process to terminate due to out-of-memory conditions or triggering operating-level kill signals that disrupt availability for all users relying on the platform.
From a security classification perspective, this vulnerability aligns with CWE-787: Out-of-bounds Read and CWE-400: Uncontrolled Resource Consumption. The exploitation vector is classified under MITRE ATT&CK technique T1529: System Shutdown or Reboot, as the ultimate goal of such an attack is to deny service by crashing the application process. While authentication is required to access this endpoint, which mitigates some risk vectors associated with unauthenticated attacks, it does not eliminate the threat for legitimate users whose credentials may be compromised or who might inadvertently trigger excessive loads through malformed data inputs.
To mitigate this vulnerability, immediate upgrade to Vikunja version 2.6.0 or later is required, as these versions implement proper limits on row cardinality and resource consumption during CSV parsing. In environments where upgrading is not immediately feasible, administrators should consider implementing network-level controls such as rate limiting or request size restrictions at the reverse proxy or load balancer layer to cap the maximum allowable payload size for migration endpoints. Additionally, configuring application-level memory limits via container orchestration tools like Kubernetes can provide a safety net by automatically restarting processes that exceed defined resource thresholds, thereby preserving overall service availability even if individual requests cause temporary crashes.