Summary
Angular Expressions - Remote Code Execution
Workarounds
A temporary workaround might be either to :
- disable user-controlled input that will be fed into angular-expressions in your application
OR
- allow only following characters in the userControlledInput :
if (/^[|a-zA-Z.0-9 :"'+-?]+$/.test(userControlledInput)) {
var result = expressions.compile(userControlledInput);
}
else {
result = undefined;
}
References
Removal of angular-expression sandbox
For more information
If you have any questions or comments about this advisory:
- Open an issue in angular-expressions
- Email us
Credits
The issue was reported by Maxime Nadeau from GoSecure, Inc.
Impact
The vulnerability, reported by GoSecure Inc, allows Remote Code Execution, if you call expressions.compile(userControlledInput) where userControlledInput is text that comes from user input.
This time, the security of the package could be bypassed by using a more complex payload, using a .constructor.constructor technique.
- If running angular-expressions in the browser, an attacker could run any browser script when the application code calls expressions.compile(userControlledInput).
- If running angular-expressions on the server, an attacker could run any Javascript expression, thus gaining Remote Code Execution.
Untrusted input is evaluated as executable code within the application's runtime environment. Typical impact: arbitrary code execution within the application's privilege context.
CVE-2021-21277 has a CVSS score of 8.8 (High). The vector is network-reachable, low 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 (1.1.2); upgrading removes the vulnerable code path.
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.
Already deployed Kodem?
See it in your environmentNew to Kodem? Get a demo →Remediation advice
Users should upgrade to version 1.1.2 of angular-expressions
Frequently Asked Questions
- What is CVE-2021-21277? CVE-2021-21277 is a high-severity code injection vulnerability in angular-expressions (npm), affecting versions < 1.1.2. It is fixed in 1.1.2. Untrusted input is evaluated as executable code within the application's runtime environment.
- How severe is CVE-2021-21277? CVE-2021-21277 has a CVSS score of 8.8 (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 angular-expressions are affected by CVE-2021-21277? angular-expressions (npm) versions < 1.1.2 is affected.
- Is there a fix for CVE-2021-21277? Yes. CVE-2021-21277 is fixed in 1.1.2. Upgrade to this version or later.
- Is CVE-2021-21277 exploitable, and should I be worried? Whether CVE-2021-21277 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-2021-21277 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-2021-21277? Upgrade
angular-expressionsto 1.1.2 or later.