CVE-2026-42154: Prometheus

High severity, CVSS 7.5. EPSS: 0.9% chance of exploitation in the next 30 days.

Prometheus is an open-source monitoring system and time series database. Prior to versions 3.5.3 and 3.11.3, 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. This issue has been patched in versions 3.5.3 and 3.11.3.

Affected products

• Prometheus Prometheus: before 3.5.3 (fixed in 3.5.3); from 3.6.0, before 3.11.3 (fixed in 3.11.3)

Published 2026-05-04. Last modified 2026-09-10.