CVE-2023-44487 is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in golang.org/x/net. 20 public exploit references exist, so weaponization risk is real. O3 Security confirms whether CVE-2023-44487 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
HTTP/2 Stream Cancellation Attack
Exploitation Status
Actively exploited in the wild
- CISA’s SSVC triage classifies this CVE as under active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2023-44487.
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-2023-44487 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE sits: patch-first territory.
Where this sits among everything scored
Of 368,770 CVEs with a current EPSS score, this one falls in the ≥ 90% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
golang.org/x/net☕org.apache.tomcat:tomcat-coyote☕org.apache.tomcat:tomcat-coyote☕org.apache.tomcat:tomcat-coyote☕org.apache.tomcat:tomcat-coyote☕org.apache.tomcat.embed:tomcat-embed-core☕org.apache.tomcat.embed:tomcat-embed-core☕org.apache.tomcat.embed:tomcat-embed-core+14 moreReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go, Maven packages — download data is not available via public APIs for these ecosystems.
Description
The HTTP/2 protocol allows a denial of service (server resource consumption) because request cancellation can reset many streams quickly, as exploited in the wild in August through October 2023.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | golang.org/x/net | all versions | 0.17.0 |
| ☕Maven | org.apache.tomcat:tomcat-coyote | ≥ 11.0.0-M1&&< 11.0.0-M12 | 11.0.0-M12 |
| ☕Maven | org.apache.tomcat:tomcat-coyote | ≥ 10.0.0&&< 10.1.14 | 10.1.14 |
| ☕Maven | org.apache.tomcat:tomcat-coyote | ≥ 9.0.0&&< 9.0.81 | 9.0.81 |
| ☕Maven | org.apache.tomcat:tomcat-coyote | ≥ 8.5.0&&< 8.5.94 | 8.5.94 |
| ☕Maven | org.apache.tomcat.embed:tomcat-embed-core | ≥ 11.0.0-M1&&< 11.0.0-M12 | 11.0.0-M12 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
HTTP/2 2.0 - Denial Of Service (DOS)
by Madhusudhan Rajappa · Sep 16, 2025
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for golang.org/x/net. 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 golang.org/x/net to 0.17.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-44487 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-2023-44487 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-2023-44487. 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.
NGINX has been marked as Moderate Impact because, for performance and resource consumption reasons, NGINX limits the number of concurrent streams to a default of 128. In addition, to optimally balance network and server performance, NGINX allows the client to persist HTTP connections for up to 1000 requests by default…
Frequently Asked Questions
Is CVE-2023-44487 in your dependencies?
O3 detects CVE-2023-44487 across Go, Maven, SwiftURL dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.