Summary
RandomAlphaNumeric and CryptoRandomAlphaNumeric are not as random as they should be
Workarounds
If you cannot upgrade to v1.1.1, you can work around the issue by calling RandomAlphaNumericCustom(N, true, true)|CryptoRandomAlphaNumericCustom(N, true, true) instead. (Where N is the desired length, and true is the literal boolean true.)
Impact
A security-sensitive bug was discovered by Open Source Developer Erik Sundell of Sundell Open Source Consulting AB.
The functions RandomAlphaNumeric(int) and CryptoRandomAlphaNumeric(int) are not as random as they should be. Small values of int in the functions above will return a smaller subset of results than they should. For example, RandomAlphaNumeric(1) will always return a digit in the 0-9 range, while RandomAlphaNumeric(4) will return around ~7 million of the ~13M possible permutations.
This is considered a security release because programs that rely upon random generators for passwords are at an increased risk of brute force-style password guessing. There is also a higher probability of collision.
The problem was the result of a mistaken regular expression that only accepted random strings if they contained a digit from [0-9]. That restriction has been removed.
Affected versions
Security releases
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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This issue has been corrected in v1.1.1.
Frequently Asked Questions
- What is CVE-2021-4238? CVE-2021-4238 is a low-severity security vulnerability in github.com/Masterminds/goutils (go), affecting versions < 1.1.1. It is fixed in 1.1.1.
- Which versions of github.com/Masterminds/goutils are affected by CVE-2021-4238? github.com/Masterminds/goutils (go) versions < 1.1.1 is affected.
- Is there a fix for CVE-2021-4238? Yes. CVE-2021-4238 is fixed in 1.1.1. Upgrade to this version or later.
- Is CVE-2021-4238 exploitable, and should I be worried? Whether CVE-2021-4238 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-2021-4238 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-2021-4238? Upgrade
github.com/Masterminds/goutilsto 1.1.1 or later.