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
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
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-42154 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,156 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
github.com/prometheus/prometheus🐹github.com/prometheus/prometheus🐹github.com/prometheus/prometheusReal-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
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/prometheus/prometheus | ≥ 0.306.0&&< 0.311.3 | 0.311.3go get github.com/prometheus/prometheus@v0.311.3 |
| 🐹Go | github.com/prometheus/prometheus | all versions | 0.305.2go get github.com/prometheus/prometheus@v0.305.2 |
| 🐹Go | github.com/prometheus/prometheus | ≥ 1.0.0-rc.0 | No fix |
Detection & mitigation playbook
Open-source dependencyDetect
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
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-42154 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-42154. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
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.
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…
| 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 for Red Hat OpenShift 6 | openshift-logging/loki-rhel9-operator:1785418915 | RHSA-2026:50843 |
Frequently Asked Questions
Is CVE-2026-42154 in your dependencies?
O3 Security finds CVE-2026-42154 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.