What is CVE-2021-31402?

CVE-2021-31402 is a high-severity security vulnerability in dio (pub), affecting versions < 5.0.0. It is fixed in 5.0.0.

How severe is CVE-2021-31402?

CVE-2021-31402 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 dio are affected by CVE-2021-31402?

dio (pub) versions < 5.0.0 is affected.

Is there a fix for CVE-2021-31402?

Yes. CVE-2021-31402 is fixed in 5.0.0. Upgrade to this version or later.

Is CVE-2021-31402 exploitable, and should I be worried?

Whether CVE-2021-31402 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-2021-31402 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-2021-31402 in dio

Q: How severe is CVE-2021-31402?

CVE-2021-31402 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 dio are affected by CVE-2021-31402?

dio (pub) versions < 5.0.0 is affected.

Q: Is there a fix for CVE-2021-31402?

Yes. CVE-2021-31402 is fixed in 5.0.0. Upgrade to this version or later.

Q: Is CVE-2021-31402 exploitable, and should I be worried?

Whether CVE-2021-31402 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-2021-31402 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

dio vulnerable to CRLF injection with HTTP method string

Workarounds

Cherry-pick the commit to your own fork can resolves the vulberability too.

References

Impact

The dio package 4.0.0 for Dart allows CRLF injection if the attacker controls the HTTP method string, a different vulnerability than CVE-2020-35669.

CVE-2021-31402 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 (5.0.0); upgrading removes the vulnerable code path.

Affected versions

dio (< 5.0.0)

Security releases

dio → 5.0.0 (pub)

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

The vulnerability has been resolved by https://github.com/cfug/dio/commit/927f79e93ba39f3c3a12c190624a55653d577984, and included since v5.0.0.

Frequently Asked Questions

What is CVE-2021-31402? CVE-2021-31402 is a high-severity security vulnerability in dio (pub), affecting versions < 5.0.0. It is fixed in 5.0.0.
How severe is CVE-2021-31402? CVE-2021-31402 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 dio are affected by CVE-2021-31402? dio (pub) versions < 5.0.0 is affected.
Is there a fix for CVE-2021-31402? Yes. CVE-2021-31402 is fixed in 5.0.0. Upgrade to this version or later.
Is CVE-2021-31402 exploitable, and should I be worried? Whether CVE-2021-31402 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-2021-31402 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-2021-31402? Upgrade dio to 5.0.0 or later.