Alertmanager can expose local files content via specially crafted config

Vulnerability Description

Cortex provides multi-tenant, long term storage for Prometheus. A local file inclusion vulnerability exists in Cortex versions 1.13.0, 1.13.1 and 1.14.0, where a malicious actor could remotely read local files as a result of parsing maliciously crafted Alertmanager configurations when submitted to the Alertmanager Set Configuration API. Only users of the Alertmanager service where `-experimental.alertmanager.enable-api` or `enable_api: true` is configured are affected. Affected Cortex users are advised to upgrade to patched versions 1.13.2 or 1.14.1. However as a workaround, Cortex administrators may reject Alertmanager configurations containing the `api_key_file` setting in the `opsgenie_configs` section before sending to the Set Alertmanager Configuration API.

References

• https://github.com/cortexproject/cortex/security/advisories/GHSA-cq2g-pw6q-hf7j
• https://cortexmetrics.io/docs/api/#set-alertmanager-configuration
• https://github.com/cortexproject/cortex/releases/tag/v1.13.2
• https://github.com/cortexproject/cortex/releases/tag/v1.14.1