CVE-2021-39204 — pomerium
HIGHCVE-2021-39204 is a high-severity (CVSS 7.5) CWE-834 vulnerability in github.com/pomerium/pomerium. A fix is available for github.com/pomerium/pomerium — see the affected versions and patch details below.
Excessive CPU usage
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-2021-39204 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/pomerium/pomerium🐹github.com/pomerium/pomeriumReal-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
Envoy, which Pomerium is based on, incorrectly handles resetting of HTTP/2 streams with excessive complexity. This can lead to high CPU utilization when a large number of streams are reset.
Impact
This can result in a DoS condition.
Patches
Pomerium versions 0.14.8 and 0.15.1 contain an upgraded envoy binary with this vulnerability patched.
Workarounds
N/A
References
envoy GSA envoy CVE envoy announcement
For more information
If you have any questions or comments about this advisory:
- Open an issue in pomerium/pomerium
- Email us at [email protected]
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/pomerium/pomerium | all versions | 0.14.8go get github.com/pomerium/pomerium@v0.14.8 |
| 🐹Go | github.com/pomerium/pomerium | ≥ 0.15.0&&< 0.15.1 | 0.15.1go get github.com/pomerium/pomerium@v0.15.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/pomerium/pomerium, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/pomerium/pomerium to 0.14.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-39204 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-2021-39204 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2021-39204. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2021-39204 in your dependencies?
O3 Security finds CVE-2021-39204 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.