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CRITICAL severity

CVE-2018-12542 — vertx-web

CRITICALFix: vert-x3/vertx-web@57a65dc

CVE-2018-12542 is a critical-severity (CVSS 9.8) Path Traversal vulnerability in io.vertx:vertx-web. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for io.vertx:vertx-web — see the affected versions and patch details below.

Eclipse Vert.x does not properly neutralize '' (forward slashes) sequences that can resolve to an external location

Also known asGHSA-h39x-m55c-v55h
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
1 known
Exploitation data as of Nov 2, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
2.2%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs83th percentile — riskier than 83% of all scored CVEsHighest risk
0.38%1.18%1.98%2.79%0.9%2.2%May 26Sep 26Nov 26

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
☕io.vertx:vertx-web

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

In version from 3.0.0 to 3.5.3 of Eclipse Vert.x, the StaticHandler uses external input to construct a pathname that should be within a restricted directory, but it does not properly neutralize '' (forward slashes) sequences that can resolve to a location that is outside of that directory when running on Windows Operating Systems.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
☕Mavenio.vertx:vertx-web≥ 3.0.0&&< 3.5.43.5.4io.vertx:vertx-web:3.5.4

Affected Products

1 product · 1 configurations
Application
vert.xeclipse
≥ 3.0.0 && ≤ 3.5.3
range
Exploits & PoCs
1

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

In version from 3.0.0 to 3.5.3 of Eclipse Vert.x, the StaticHandler uses…

github.comNVDDec 2020

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.vertx:vertx-web, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update io.vertx:vertx-web to 3.5.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2018-12542 is resolved across your whole dependency graph.

  3. 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

In version from 3.0.0 to 3.5.3 of Eclipse Vert.x, the StaticHandler uses external input to construct a pathname that should be within a restricted directory, but it does not properly neutralize '\' (forward slashes) sequences that can resolve to a location that is outside of that directory when running on Windows Operating Systems.
O3 Security · Impact-Aware SCA

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CVE-2018-12542: vertx-web — Fixed in 3.5.4