CVE-2026-42154: Prometheus: remote read endpoint allows denial of service via crafted snappy payload

Vulnerability summary

CVE-2026-42154 is a high (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in prometheus. EPSS estimates a 0.81% chance of exploitation in the next 30 days, higher than 57% of scored vulnerabilities.

Timeline

1. 04-05-2026
   PublishedVulnerability first disclosed.
2. 10-09-2026
   Last modifiedVulnerability information updated.

Description

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.

• CWE-400Uncontrolled Resource ConsumptionThe product does not properly control the allocation and maintenance of a limited resource.
• CWE-789Memory Allocation with Excessive Size ValueThe product allocates memory based on an untrusted, large size value, but it does not ensure that the size is within expected limits, allowing arbitrary amounts of memory to be allocated.
• CWE-770Allocation of Resources Without Limits or ThrottlingThe product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.