Kubeflow Pipelines: Pipeline archive upload allows decompression bomb to exhaust server memory

## Summary The Kubeflow Pipelines API server decompresses uploaded pipeline archives without adequately bounding expanded data in affected versions. A small ZIP or gzip-compressed tar archive can consume disproportionately large amounts of memory while the server locates or reads the pipeline file, potentially exhausting API-server resources and interrupting service. Multipart pipeline and pipeline-version upload processing decompresses the archive before namespace authorization, so a caller who can reach those endpoints does not need a successful pipeline-create authorization decision to trigger the issue. External authentication and network controls can restrict reachability. URL-import handlers authorize before fetching and decompressing a remote archive. The amount of expansion needed to exhaust memory depends on deployment resource limits and concurrent activity; no particular archive is guaranteed to crash every deployment. ## Remediation Upgrade the API server to **[Kubeflow Pipelines 2.18.0](https://github.com/kubeflow/pipelines/releases/tag/2.18.0)**. Versions through 2.17.3 are affected; the first affected release has not been established. [PR #14171](https://github.com/kubeflow/pipelines/pull/14171) bounds compressed input and extracted pipeline data. [PR #14186](https://github.com/kubeflow/pipelines/pull/14186) strengthens the total tar traversal budget, including metadata and skipped entries. The 2.18 release also includes configurable upload and specification limits; operators should review the shipped settings and resource budget. These controls address pipeline archive amplification and do not establish general HTTP-body, temporary-disk, concurrency, or CPU limits. Until upgrading, restrict access to upload and import endpoints and apply deployment-level request and resource controls. A compressed upload-size limit alone does not prevent decompression amplification. Regression tests cover compressed input, selected-entry boundaries, and tar traversal budgets; no deployed-server OOM test was performed for this assessment. ## Credit [bugbunny.ai](https://bugbunny.ai) discovered and reported the issue. Ayush Gupta ([@Ayush-kathil](https://github.com/Ayush-kathil)) authored the archive fixes in #14171 and #14186, with Jeff Spahr ([@jeffspahr](https://github.com/jeffspahr)) contributing regression coverage to #14171. [@BrianWillows](https://github.com/BrianWillows) later submitted a mixed report that included source analysis of pipeline-archive decompression.