CVE-2021-43795 is a high-severity (CVSS 7.5) Path Traversal vulnerability in com.linecorp.armeria:armeria. A fix is available for com.linecorp.armeria:armeria — see the affected versions and patch details below.
Path Traversal in com.linecorp.armeria:armeria
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-2021-43795 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 377,636 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
com.linecorp.armeria:armeriaReal-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
Impact
An attacker can access an Armeria server's local file system beyond its restricted directory by sending an HTTP request whose path contains %2F (encoded /), such as /files/..%2Fsecrets.txt, bypassing Armeria's path validation logic.
Patches
Armeria 1.13.4 or above contains the hardened path validation logic that handles %2F properly.
Workarounds
This vulnerability can be worked around by inserting a decorator that performs an additional validation on the request path, e.g.
Server
.builder()
.serviceUnder(
"/files",
FileService
.of(...)
.decorate((delegate, ctx, req) -> {
String path = req.headers().path();
if (path.contains("%2f") || path.contains("%2F")) {
return HttpResponse.of(HttpStatus.BAD_REQUEST);
}
return delegate.serve(ctx, req);
})
)
.build()
For more information
If you have any questions or comments about this advisory:
- Open an issue in line/armeria
- Chat with us at Slack
Credits
This vulnerability was originally reported by Abdallah Zaher (elcayser-0x0a).
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | com.linecorp.armeria:armeria | ≥ 1.12.0&&< 1.13.4 | 1.13.4com.linecorp.armeria:armeria:1.13.4 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for com.linecorp.armeria:armeria, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update com.linecorp.armeria:armeria to 1.13.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-43795 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-2021-43795 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2021-43795. 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-2021-43795 in your dependencies?
O3 Security finds CVE-2021-43795 across Maven dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.