Apache Kyuubi CVE-2026-52680

Exploitation requires network access to Apache Kyuubi's REST API batch submission (multipart upload) endpoint on an affected version (1.7.0-1.11.1); the attacker must be able to send a multipart/form-data request with a crafted 'filename' containing path traversal sequences. The official CVSS vector is PR:N/UI:N, implying no authentication or user interaction against a reachable endpoint, though in deployments that gate the REST API behind Kyuubi authentication the attacker would first need valid REST access - verify whether your instance exposes the batch endpoint unauthenticated. What limits impact: the write is 'subject to filesystem permissions,' so the OS user running Kyuubi must have write access to the targeted destination path for the traversal to succeed, and turning a file write into code execution or data compromise requires a suitable target file (executable script, sourced config, or served content).

The signals are mixed and warrant a nuanced priority call. The vendor/NVD CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H, base 9.8) treats this as unauthenticated, network-reachable, low-complexity with full CIA impact - consistent with an arbitrary file-write that can escalate to code execution or config tampering. However EPSS is only 0.28% (21st percentile), it is NOT on CISA KEV, and no POC is referenced, so there is no evidence of active or imminent mass exploitation. A key caveat: the CVSS rates C:H/I:H/A:H, but the described primitive is fundamentally an integrity issue (writing controlled content); confidentiality and availability impact are realized only through escalation (e.g. overwriting a config or a script that later executes), which is 'subject to filesystem permissions' per the vendor - so real-world impact depends heavily on how the Kyuubi process is privileged and whether the REST endpoint is authentication-gated in the target deployment. Net: a genuinely serious, patch-now flaw for any internet- or tenant-exposed Kyuubi REST server, but the low EPSS and absence of KEV/POC mean it is not yet under broad opportunistic attack.

An attacker who can reach the Kyuubi REST batch upload endpoint submits a multipart POST whose file part sets filename to something like '../../../../opt/kyuubi/conf/malicious' or a path that later gets executed or sourced by the service. The server writes the attacker-controlled bytes outside the upload directory, and if the process has write access to a script, config, or web-served location, the attacker can pivot to configuration tampering or code execution. No POC is referenced, and success depends on the server process's filesystem permissions.