How severe is CVE-2021-43795?

CVE-2021-43795 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2021-43795?

CVE-2021-43795 affects the following packages: com.linecorp.armeria:armeria (Maven). Ecosystems affected: Maven.

How do I fix CVE-2021-43795?

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.

How do I detect CVE-2021-43795 in my Maven dependencies?

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.

How do I mitigate CVE-2021-43795 if there is no patch (or I can't update yet)?

Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.

Is CVE-2021-43795 actively exploited in the wild?

No public exploit code has been indexed for CVE-2021-43795 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2021-43795?

CVE-2021-43795 has an EPSS (Exploit Prediction Scoring System) score of 1.7%, placing it in the 77th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2021-43795?

CVE-2021-43795 is classified as Path Traversal (CWE-22). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2021-43795 published, and has it been updated?

CVE-2021-43795 was published on December 2, 2021 and was last updated on October 20, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕

☕ Maven

Not in CISA KEV

HIGH severity

CVE-2021-43795 — armeria

HIGHFix: line/armeria@e2697a5

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

Also known asGHSA-8fp4-rp6c-5gcv

Published

Dec 2, 2021

Updated

Oct 20, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 3, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

1.7%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs77th percentile — riskier than 77% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

☕com.linecorp.armeria:armeria

Real-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

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`com.linecorp.armeria:armeria`	≥ 1.12.0&&< 1.13.4	1.13.4`com.linecorp.armeria:armeria:1.13.4`

Affected Products

1 product · 1 configurations

Application

armerialinecorp

< 1.13.4

range

Detection & mitigation playbook

Open-source dependency

Detect
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
Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.

Frequently Asked Questions

### 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. ```java Server .builder() .serviceUnder( "/files", FileService .of(...