CVE-2026-42154

A flaw was found in Prometheus. An unauthenticated attacker can exploit the remote read endpoint (/api/v1/read) by sending a specially crafted, small snappy-compressed payload. This payload causes a disproportionately large memory allocation, leading to memory exhaustion and a Denial of Service (DoS) by crashing the Prometheus process.

This is an Important denial of service vulnerability in Prometheus, allowing an unauthenticated remote attacker to crash the Prometheus process. This could lead to service unavailability in Red Hat products that deploy Prometheus for monitoring, as the remote read endpoint does not properly validate snappy-compressed request lengths.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this issue, restrict network access to the Prometheus remote read endpoint (/api/v1/read). Configure firewall rules or network policies to permit connections only from trusted internal networks or authorized clients. This action reduces the attack surface by limiting exposure to unauthenticated remote attackers. A service restart or reload may be required for the changes to take effect.