CVE-2021-29504 is a high-severity (CVSS 7.4) CWE-295 vulnerability in wp-cli/wp-cli. O3 Security confirms whether CVE-2021-29504 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Improper Certificate Validation in WP-CLI framework
Real-World Exposure
wp-cli/wp-cliReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
WP-CLI is the command-line interface for WordPress. 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. 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. 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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | wp-cli/wp-cli | ≥ 0.12.0&&< 2.5.0 | 2.5.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for wp-cli/wp-cli. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update wp-cli/wp-cli to 2.5.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-29504 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2021-29504 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2021-29504. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2021-29504 in your dependencies?
O3 detects CVE-2021-29504 across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.