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

High7.5CVE-2026-42154 · Published May 5, 2026 · updated Sep 10, 2026

### 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.