What is CVE-2020-25739?

CVE-2020-25739 is a medium-severity cross-site scripting (XSS) vulnerability in gon (rubygems), affecting versions < 6.4.0. It is fixed in 6.4.0. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.

How severe is CVE-2020-25739?

CVE-2020-25739 has a CVSS score of 6.1 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.

Which versions of gon are affected by CVE-2020-25739?

gon (rubygems) versions < 6.4.0 is affected.

Is there a fix for CVE-2020-25739?

Yes. CVE-2020-25739 is fixed in 6.4.0. Upgrade to this version or later.

Is CVE-2020-25739 exploitable, and should I be worried?

Whether CVE-2020-25739 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

What actually determines whether CVE-2020-25739 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

CVE-2020-25739 in gon

Q: How severe is CVE-2020-25739?

CVE-2020-25739 has a CVSS score of 6.1 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.

Q: Which versions of gon are affected by CVE-2020-25739?

gon (rubygems) versions < 6.4.0 is affected.

Q: Is there a fix for CVE-2020-25739?

Yes. CVE-2020-25739 is fixed in 6.4.0. Upgrade to this version or later.

Q: Is CVE-2020-25739 exploitable, and should I be worried?

Whether CVE-2020-25739 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

Q: What actually determines whether CVE-2020-25739 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

Summary

Gon gem lack of escaping certain input when outputting as JSON

An issue was discovered in the gon gem before gon-6.4.0 for Ruby. MultiJson does not honor the escape_mode parameter to escape fields as an XSS protection mechanism. To mitigate, json_dumper.rb in gon now does escaping for XSS by default without relying on MultiJson.

Impact

Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.

CVE-2020-25739 has a CVSS score of 6.1 (Medium). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (6.4.0); upgrading removes the vulnerable code path.

Affected versions

gon (< 6.4.0)

Security releases

gon → 6.4.0 (rubygems)

Kodem intelligence

Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.

Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.

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Remediation advice

Upgrade gon to 6.4.0 or later to resolve this vulnerability.

Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.

Frequently Asked Questions

What is CVE-2020-25739? CVE-2020-25739 is a medium-severity cross-site scripting (XSS) vulnerability in gon (rubygems), affecting versions < 6.4.0. It is fixed in 6.4.0. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
How severe is CVE-2020-25739? CVE-2020-25739 has a CVSS score of 6.1 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
Which versions of gon are affected by CVE-2020-25739? gon (rubygems) versions < 6.4.0 is affected.
Is there a fix for CVE-2020-25739? Yes. CVE-2020-25739 is fixed in 6.4.0. Upgrade to this version or later.
Is CVE-2020-25739 exploitable, and should I be worried? Whether CVE-2020-25739 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
What actually determines whether CVE-2020-25739 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
How do I fix CVE-2020-25739? Upgrade gon to 6.4.0 or later.