How severe is CVE-2026-42154?

CVE-2026-42154 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2026-42154?

CVE-2026-42154 affects the following packages: github.com/prometheus/prometheus (Go), github.com/prometheus/prometheus (Go), github.com/prometheus/prometheus (Go). Ecosystems affected: Go.

How do I fix CVE-2026-42154?

Update github.com/prometheus/prometheus to 0.311.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42154 is resolved across your whole dependency graph.

How do I detect CVE-2026-42154 in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/prometheus/prometheus, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-42154 if there is no patch (or I can't update yet)?

Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Is CVE-2026-42154 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-42154 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-42154?

CVE-2026-42154 has an EPSS (Exploit Prediction Scoring System) score of 0.8%, placing it in the 57th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-42154?

CVE-2026-42154 is classified as Uncontrolled Resource Consumption (CWE-400), CWE-789 (CWE-789), CWE-770 (CWE-770). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-42154 published, and has it been updated?

CVE-2026-42154 was published on May 4, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹

🐹 Go

Not in CISA KEV

HIGH severity

CVE-2026-42154 — prometheus

HIGHFix: prometheus/prometheus#18584

CVE-2026-42154 is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in github.com/prometheus/prometheus. A fix is available for github.com/prometheus/prometheus — see the affected versions and patch details below.

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

Also known asBIT-prometheus-2026-42154GHSA-8rm2-7qqf-34qmGO-2026-5264

Published

May 4, 2026

Updated

Oct 28, 2026

Affected

3 pkgs

Patched

2 / 3

Exploits

None indexed

Exploitation data as of Nov 7, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-42154.

EPSS Exploitation Probability

via FIRST.org ↗

0.8%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs57th percentile — riskier than 57% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

3 pkgs affected

🐹github.com/prometheus/prometheus🐹github.com/prometheus/prometheus🐹github.com/prometheus/prometheus

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

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.

Affected Packages

3 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/prometheus/prometheus`	≥ 0.306.0&&< 0.311.3	0.311.3`go get github.com/prometheus/prometheus@v0.311.3`
🐹Go	`github.com/prometheus/prometheus`	all versions	0.305.2`go get github.com/prometheus/prometheus@v0.305.2`
🐹Go	`github.com/prometheus/prometheus`	≥ 1.0.0-rc.0	No fix

Affected Products

1 product · 2 configurations

Application

prometheusprometheus

≥ 3.6.0 && < 3.11.3

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/prometheus/prometheus, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/prometheus/prometheus to 0.311.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42154 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant

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…

Workaround published by Red Hat

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.

Source: Red Hat security advisory for CVE-2026-42154 (CC BY 4.0)

Product	Fixed in	Advisory
Red Hat Enterprise Linux 10	`opentelemetry-collector-0:0.152.1-1.el10_2`	RHSA-2026:34357
Red Hat Enterprise Linux 10.0 Extended Update Support	`opentelemetry-collector-0:0.152.1-1.el10_0`	RHSA-2026:53413
Red Hat Enterprise Linux 9	`opentelemetry-collector-0:0.152.1-1.el9_8`	RHSA-2026:34359
Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions	`opentelemetry-collector-0:0.152.1-1.el9_4`	RHSA-2026:53412
Red Hat Enterprise Linux 9.6 Extended Update Support	`opentelemetry-collector-0:0.152.1-1.el9_6`	RHSA-2026:53415
RHEM 1.0 for RHEL 9	`flightctl-0:1.0.3-1.el9em`	RHSA-2026:36796
RHEM 1.1 for RHEL 10	`flightctl-0:1.1.3-1.el10em`	RHSA-2026:41019
Logging Subsystem for Red Hat OpenShift 6.0	`openshift-logging/loki-rhel9-operator:1785418915`	RHSA-2026:50843

Frequently Asked Questions

### 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 pr

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