What is CVE-2021-29504?

CVE-2021-29504 is a critical-severity security vulnerability in wp-cli/wp-cli (composer), affecting versions >= 0.12.0, < 2.5.0. It is fixed in 2.5.0.

How severe is CVE-2021-29504?

CVE-2021-29504 has a CVSS score of 9.1 (Critical). 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 wp-cli/wp-cli are affected by CVE-2021-29504?

wp-cli/wp-cli (composer) versions >= 0.12.0, < 2.5.0 is affected.

Is there a fix for CVE-2021-29504?

Yes. CVE-2021-29504 is fixed in 2.5.0. Upgrade to this version or later.

Is CVE-2021-29504 exploitable, and should I be worried?

Whether CVE-2021-29504 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-2021-29504 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-2021-29504?

Upgrade wp-cli/wp-cli to 2.5.0 or later.

CVE-2021-29504 in wp-cli/wp-cli

Q: How severe is CVE-2021-29504?

CVE-2021-29504 has a CVSS score of 9.1 (Critical). 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 wp-cli/wp-cli are affected by CVE-2021-29504?

wp-cli/wp-cli (composer) versions >= 0.12.0, < 2.5.0 is affected.

Q: Is there a fix for CVE-2021-29504?

Yes. CVE-2021-29504 is fixed in 2.5.0. Upgrade to this version or later.

Q: Is CVE-2021-29504 exploitable, and should I be worried?

Whether CVE-2021-29504 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-2021-29504 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-2021-29504?

Upgrade wp-cli/wp-cli to 2.5.0 or later.

Summary

Improper Certificate Validation in WP-CLI framework

Workarounds

There is no direct workaround for the default insecure behavior of wp-cli/wp-cli versions before 2.5.0.

The workaround for dealing with the breaking change in the commands directly affected by the new secure default behavior is to add the --insecure flag to manually opt-in to the previous insecure behavior.

References

CWE: Improper Certificate Validation

For more information

If you have any questions or comments about this advisory:

Join the #cli channel in the WordPress.org Slack to ask questions or provide feedback.

Impact

An improper error handling in HTTPS requests management in WP-CLI version 0.12.0 and later allows remote attackers able to intercept the communication to remotely disable the certificate verification on WP-CLI side, gaining full control over the communication content, including the ability to impersonate update servers and push malicious updates towards WordPress instances controlled by the vulnerable WP-CLI agent, or push malicious updates toward WP-CLI itself.

CVE-2021-29504 has a CVSS score of 9.1 (Critical). 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 (2.5.0); upgrading removes the vulnerable code path.

Affected versions

wp-cli/wp-cli (>= 0.12.0, < 2.5.0)

Security releases

wp-cli/wp-cli → 2.5.0 (composer)

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 stems from the fact that the default behavior of WP_CLI\Utils\http_request() when encountering a TLS handshake error is to disable certificate validation and retry the same request.

The default behavior has been changed with version 2.5.0 of WP-CLI and the wp-cli/wp-cli framework (via https://github.com/wp-cli/wp-cli/pull/5523) so that the WP_CLI\Utils\http_request() method accepts an $insecure option that is false by default and consequently that a TLS handshake failure is a hard error by default. This new default is a breaking change and ripples through to all consumers of WP_CLI\Utils\http_request(), including those in separate WP-CLI bundled or third-party packages.

https://github.com/wp-cli/wp-cli/pull/5523 has also added an --insecure flag to the cli update command to counter this breaking change.

Subsequent PRs on the command repositories have added an --insecure flag to the appropriate commands on the following repositories to counter the breaking change:

Frequently Asked Questions

What is CVE-2021-29504? CVE-2021-29504 is a critical-severity security vulnerability in wp-cli/wp-cli (composer), affecting versions >= 0.12.0, < 2.5.0. It is fixed in 2.5.0.
How severe is CVE-2021-29504? CVE-2021-29504 has a CVSS score of 9.1 (Critical). 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 wp-cli/wp-cli are affected by CVE-2021-29504? wp-cli/wp-cli (composer) versions >= 0.12.0, < 2.5.0 is affected.
Is there a fix for CVE-2021-29504? Yes. CVE-2021-29504 is fixed in 2.5.0. Upgrade to this version or later.
Is CVE-2021-29504 exploitable, and should I be worried? Whether CVE-2021-29504 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-2021-29504 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-2021-29504? Upgrade wp-cli/wp-cli to 2.5.0 or later.