CVE-2021-39206 — pomerium
HIGHCVE-2021-39206 is a high-severity (CVSS 8.6) CWE-863 vulnerability in github.com/pomerium/pomerium. A fix is available for github.com/pomerium/pomerium — see the affected versions and patch details below.
Incorrect Authorization with specially crafted requests
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-2021-39206 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 378,567 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, contains two authorization related vulnerabilities:
- CVE-2021-32777: incorrectly transform a URL containing a
#fragmentelement, causing a mismatch in path-prefix based authorization decisions. - CVE-2021-32779: incorrectly handle duplicate headers, dropping all but the last. This may lead to incorrect routing or authorization policy decisions.
Impact
With specially crafted requests, incorrect authorization or routing decisions may be made by Pomerium.
Patches
Pomerium v0.14.8 and v0.15.1 contain an upgraded envoy binary with these vulnerabilities patched.
Workarounds
- This issue can only be triggered when using path prefix based policy. Removing any such policies should provide mitigation.
References
envoy GSA CVE-2021-32777 envoy GSA CVE-2021-32779 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 | ≥ 0.11.0&&< 0.14.8 | 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-2021-39206 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-2021-39206 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2021-39206. 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-2021-39206 in your dependencies?
O3 Security finds CVE-2021-39206 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.