Prometheus: Remote read endpoint allows denial of service via crafted snappy payload

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.