Affected: Go: github.com/prometheus/prometheus

### Impact

The remote read endpoint (`/api/v1/read`) does not validate the declared decoded length in a snappy-compressed request body before allocating memory. An unauthenticated attacker can send a small payload that causes a huge heap allocation per request. Under concurrent load this can exhaust available memory and crash the Prometheus process.

### Patches _Has the problem been patched? What versions should users upgrade to?_

Fixed in 3.11.3 and 3.5.3 LTS. Users should upgrade to these versions or later.

### Workarounds User who can not upgrade can place Prometheus behind a reverse proxy or firewall that requires authentication before requests reach /api/v1/read.