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MEDIUM severity

CVE-2021-42357 — gateway-service-knoxsso

MEDIUM

CVE-2021-42357 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in org.apache.knox:gateway-service-knoxsso. A fix is available for org.apache.knox:gateway-service-knoxsso — see the affected versions and patch details below.

Cross-site Scripting in Apache Knox SSO

Also known asGHSA-vv38-4xcj-q4rw
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 7, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
2.6%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs85th percentile — riskier than 85% of all scored CVEsHighest risk
0.23%4.41%8.58%12.8%10.4%2.6%Apr 26Aug 26Oct 26

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

How urgent is this, really

CVE-2021-42357 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,386 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected
☕org.apache.knox:gateway-service-knoxsso

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

When using Apache Knox SSO prior to 1.6.1, a request could be crafted to redirect a user to a malicious page due to improper URL parsing. A request that included a specially crafted request parameter could be used to redirect the user to a page controlled by an attacker. This URL would need to be presented to the user outside the normal request flow through a XSS or phishing campaign.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
☕Mavenorg.apache.knox:gateway-service-knoxssoall versions1.6.1org.apache.knox:gateway-service-knoxsso:1.6.1

Affected Products

1 product · 1 configurations
Application
knoxapache
< 1.6.1
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

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

  2. Fix

    Update org.apache.knox:gateway-service-knoxsso to 1.6.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-42357 is resolved across your whole dependency graph.

  3. Workarounds

    Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

When using Apache Knox SSO prior to 1.6.1, a request could be crafted to redirect a user to a malicious page due to improper URL parsing. A request that included a specially crafted request parameter could be used to redirect the user to a page controlled by an attacker. This URL would need to be presented to the user outside the normal request flow through a XSS or phishing campaign.
O3 Security · Impact-Aware SCA

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CVE-2021-42357: gateway-service XSS — Fixed in 1.6.1