What is CVE-2026-42154?

CVE-2026-42154 is a high-severity uncontrolled resource consumption vulnerability in github.com/prometheus/prometheus (go), affecting versions >= 0.306.0, < 0.311.3. It is fixed in 0.311.3, 0.305.2. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.

How severe is CVE-2026-42154?

CVE-2026-42154 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.

Which versions of github.com/prometheus/prometheus are affected by CVE-2026-42154?

github.com/prometheus/prometheus (go) versions >= 0.306.0, < 0.311.3 is affected.

Is there a fix for CVE-2026-42154?

Yes. CVE-2026-42154 is fixed in 0.311.3, 0.305.2. Upgrade to this version or later.

Is CVE-2026-42154 exploitable, and should I be worried?

Whether CVE-2026-42154 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

What actually determines whether CVE-2026-42154 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

How do I fix CVE-2026-42154?

Upgrade: github.com/prometheus/prometheus to 0.311.3 or later, github.com/prometheus/prometheus to 0.305.2 or later.

CVE-2026-42154 in github.com/prometheus/prometheus | Intelligent Application Security

Q: How severe is CVE-2026-42154?

CVE-2026-42154 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.

Q: Which versions of github.com/prometheus/prometheus are affected by CVE-2026-42154?

github.com/prometheus/prometheus (go) versions >= 0.306.0, < 0.311.3 is affected.

Q: Is there a fix for CVE-2026-42154?

Yes. CVE-2026-42154 is fixed in 0.311.3, 0.305.2. Upgrade to this version or later.

Q: Is CVE-2026-42154 exploitable, and should I be worried?

Whether CVE-2026-42154 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

Q: What actually determines whether CVE-2026-42154 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

Q: How do I fix CVE-2026-42154?

Upgrade: github.com/prometheus/prometheus to 0.311.3 or later, github.com/prometheus/prometheus to 0.305.2 or later.

Summary

Workarounds

User who can not upgrade can place Prometheus behind a reverse proxy or firewall that requires authentication before requests reach /api/v1/read.

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.

Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.

CVE-2026-42154 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.311.3, 0.305.2); upgrading removes the vulnerable code path.

Affected versions

github.com/prometheus/prometheus (>= 0.306.0, < 0.311.3) github.com/prometheus/prometheus (< 0.305.2) github.com/prometheus/prometheus (>= 1.0.0-rc.0, <= 2.5.0)

Security releases

github.com/prometheus/prometheus → 0.311.3 (go) github.com/prometheus/prometheus → 0.305.2 (go)

Kodem intelligence

Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.

Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.

See it in your environment

Remediation advice

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.

Frequently Asked Questions

What is CVE-2026-42154? CVE-2026-42154 is a high-severity uncontrolled resource consumption vulnerability in github.com/prometheus/prometheus (go), affecting versions >= 0.306.0, < 0.311.3. It is fixed in 0.311.3, 0.305.2. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
How severe is CVE-2026-42154? CVE-2026-42154 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
Which versions of github.com/prometheus/prometheus are affected by CVE-2026-42154? github.com/prometheus/prometheus (go) versions >= 0.306.0, < 0.311.3 is affected.
Is there a fix for CVE-2026-42154? Yes. CVE-2026-42154 is fixed in 0.311.3, 0.305.2. Upgrade to this version or later.
Is CVE-2026-42154 exploitable, and should I be worried? Whether CVE-2026-42154 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
What actually determines whether CVE-2026-42154 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
How do I fix CVE-2026-42154?
- Upgrade github.com/prometheus/prometheus to 0.311.3 or later
- Upgrade github.com/prometheus/prometheus to 0.305.2 or later

Other vulnerabilities in github.com/prometheus/prometheus

CVE-2026-44903 CVE-2026-42154 CVE-2026-40179 CVE-2021-29622