CVE-2021-44138 — resin
HIGHCVE-2021-44138 is a high-severity (CVSS 7.5) vulnerability in com.caucho:resin. 1 public exploit reference exists, so weaponization risk is real. No vendor fix is recorded yet; mitigation options are listed below.
Path Traversal in Caucho Resin
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-2021-44138 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 10–50% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
com.caucho:resinReal-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
There is a Directory traversal vulnerability in Caucho Resin, as distributed in Resin 4.0.52 - 4.0.56, which allows remote attackers to read files in arbitrary directories via a ; in a pathname within an HTTP request.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | com.caucho:resin | ≥ 4.0.52 | No fix |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for com.caucho:resin, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Remediation status
No patched version of com.caucho:resin has shipped for CVE-2021-44138 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
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-2021-44138 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2021-44138. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
How to detect CVE-2021-44138
A community-maintained Nuclei template exists for this CVE. You can scan for it directly:
nuclei -id cve-2021-44138 -u https://target- Template
- Caucho Resin >=4.0.52 <=4.0.56 - Directory traversal
- Severity
- high
- Impact
- An attacker can exploit this vulnerability to read arbitrary files on the server, potentially leading to unauthorized access or sensitive data exposure.
- Remediation
- Upgrade Caucho Resin to a version higher than 4.0.56 to mitigate the vulnerability.
Template by ProjectDiscovery nuclei-templates (carrot2), MIT licensed. View the full template. Scan only systems you are authorised to test.
Frequently Asked Questions
Is CVE-2021-44138 in your dependencies?
O3 Security finds CVE-2021-44138 across Maven dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.