What is CVE-2017-20165?

CVE-2017-20165 is a high-severity inefficient regular expression (ReDoS) vulnerability in debug (npm), affecting versions < 2.6.9. It is fixed in 2.6.9, 3.1.0. A regular expression with worst-case exponential or polynomial matching time is applied to untrusted input, causing excessive CPU use.

How severe is CVE-2017-20165?

CVE-2017-20165 has a CVSS score of 7.5 (High). 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 debug are affected by CVE-2017-20165?

debug (npm) versions < 2.6.9 is affected.

Is there a fix for CVE-2017-20165?

Yes. CVE-2017-20165 is fixed in 2.6.9, 3.1.0. Upgrade to this version or later.

Is CVE-2017-20165 exploitable, and should I be worried?

Whether CVE-2017-20165 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-2017-20165 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-2017-20165?

Upgrade: debug to 2.6.9 or later, debug to 3.1.0 or later.

CVE-2017-20165 in debug

Q: How severe is CVE-2017-20165?

CVE-2017-20165 has a CVSS score of 7.5 (High). 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 debug are affected by CVE-2017-20165?

debug (npm) versions < 2.6.9 is affected.

Q: Is there a fix for CVE-2017-20165?

Yes. CVE-2017-20165 is fixed in 2.6.9, 3.1.0. Upgrade to this version or later.

Q: Is CVE-2017-20165 exploitable, and should I be worried?

Whether CVE-2017-20165 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-2017-20165 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.

Q: How do I fix CVE-2017-20165?

Upgrade: debug to 2.6.9 or later, debug to 3.1.0 or later.

Summary

debug Inefficient Regular Expression Complexity vulnerability

A vulnerability classified as problematic has been found in debug-js debug up to 3.0.x. This affects the function useColors of the file src/node.js. The manipulation of the argument str leads to inefficient regular expression complexity. Upgrading to version 3.1.0 is able to address this issue. The name of the patch is c38a0166c266a679c8de012d4eaccec3f944e685. It is recommended to upgrade the affected component. The identifier VDB-217665 was assigned to this vulnerability. The patch has been backported to the 2.6.x branch in version 2.6.9.

Impact

A regular expression with worst-case exponential or polynomial matching time is applied to untrusted input, causing excessive CPU use. Typical impact: denial of service when input is crafted to trigger backtracking.

CVE-2017-20165 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. 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 (2.6.9, 3.1.0); upgrading removes the vulnerable code path.

Affected versions

debug (< 2.6.9) debug (>= 3.0.0, < 3.1.0)

Security releases

debug → 2.6.9 (npm) debug → 3.1.0 (npm)

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 the following packages to resolve this vulnerability:

debug to 2.6.9 or later; debug to 3.1.0 or later

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

Frequently Asked Questions

What is CVE-2017-20165? CVE-2017-20165 is a high-severity inefficient regular expression (ReDoS) vulnerability in debug (npm), affecting versions < 2.6.9. It is fixed in 2.6.9, 3.1.0. A regular expression with worst-case exponential or polynomial matching time is applied to untrusted input, causing excessive CPU use.
How severe is CVE-2017-20165? CVE-2017-20165 has a CVSS score of 7.5 (High). 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 debug are affected by CVE-2017-20165? debug (npm) versions < 2.6.9 is affected.
Is there a fix for CVE-2017-20165? Yes. CVE-2017-20165 is fixed in 2.6.9, 3.1.0. Upgrade to this version or later.
Is CVE-2017-20165 exploitable, and should I be worried? Whether CVE-2017-20165 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-2017-20165 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-2017-20165?
- Upgrade debug to 2.6.9 or later
- Upgrade debug to 3.1.0 or later

Other vulnerabilities in debug

CVE-IDSeverityPackage summary

CVE-2025-59144Highdebug: [email protected] contains malware after npm account takeover CVE-2017-16137Lowdebug: Regular Expression Denial of Service in debug