CVE-2026-40984 is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in io.micrometer:micrometer-core. O3 Security confirms whether CVE-2026-40984 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Micrometer HTTP server instrumentations DoS
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-2026-40984.
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-2026-40984 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 0 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
io.micrometer:micrometer-core☕io.micrometer:micrometer-core☕io.micrometer:micrometer-core☕io.micrometer:micrometer-core☕io.micrometer:micrometer-core☕io.micrometer:micrometer-jetty12☕io.micrometer:micrometer-jetty12☕io.micrometer:micrometer-jetty12+5 moreReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
In Micrometer, it is possible for a user to provide specially crafted HTTP requests that may cause a denial-of-service (DoS) condition.
Affected versions: micrometer-core 1.16.0 through 1.16.5; 1.15.0 through 1.15.11; 1.14.0 through 1.14.15; 1.13.0 through 1.13.18; 1.9.0 through 1.9.17. micrometer-jetty11 1.16.0 through 1.16.5; 1.15.0 through 1.15.11; 1.14.0 through 1.14.15; 1.13.0 through 1.13.18. micrometer-jetty12 1.16.0 through 1.16.5; 1.15.0 through 1.15.11; 1.14.0 through 1.14.15; 1.13.0 through 1.13.18.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | io.micrometer:micrometer-core | ≥ 1.16.0&&< 1.16.6 | 1.16.6 |
| ☕Maven | io.micrometer:micrometer-core | ≥ 1.15.0&&< 1.15.12 | 1.15.12 |
| ☕Maven | io.micrometer:micrometer-core | ≥ 1.14.0 | No fix |
| ☕Maven | io.micrometer:micrometer-core | ≥ 1.10.0 | No fix |
| ☕Maven | io.micrometer:micrometer-core | all versions | No fix |
| ☕Maven | io.micrometer:micrometer-jetty12 | ≥ 1.16.0&&< 1.16.6 | 1.16.6 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.micrometer:micrometer-core. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update io.micrometer:micrometer-core to 1.16.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-40984 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 pinpoints whether CVE-2026-40984 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-40984. 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 Micrometer, a component present in several Red Hat products. A remote, unauthenticated attacker can exploit this flaw by sending specially crafted HTTP requests, leading to resource exhaustion and disrupting the availability of affected services. Exploitation of…
Frequently Asked Questions
Is CVE-2026-40984 in your dependencies?
O3 detects CVE-2026-40984 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.