How severe is CVE-2021-29504?

CVE-2021-29504 has a CVSS score of 7.4/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2021-29504?

CVE-2021-29504 affects the following packages: wp-cli/wp-cli (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2021-29504?

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.

How do I detect CVE-2021-29504 in my Packagist dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for wp-cli/wp-cli, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2021-29504 if there is no patch (or I can't update yet)?

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.

Is CVE-2021-29504 actively exploited in the wild?

No public exploit code has been indexed for CVE-2021-29504 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2021-29504?

CVE-2021-29504 has an EPSS (Exploit Prediction Scoring System) score of 1.3%, placing it in the 70th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2021-29504?

CVE-2021-29504 is classified as CWE-295 (CWE-295). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2021-29504 published, and has it been updated?

CVE-2021-29504 was published on June 7, 2021 and was last updated on July 9, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐘

🐘 Packagist

Not in CISA KEV

HIGH severity

CVE-2021-29504 — wp-cli

HIGHFix: wp-cli/checksum-command#86

CVE-2021-29504 is a high-severity (CVSS 7.4) CWE-295 vulnerability in wp-cli/wp-cli. A fix is available for wp-cli/wp-cli — see the affected versions and patch details below.

Improper Certificate Validation in WP-CLI framework

Also known asBIT-wp-cli-2021-29504GHSA-rwgm-f83r-v3qj

Published

Jun 7, 2021

Updated

Jul 9, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 11, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

1.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs70th percentile — riskier than 70% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2021-29504 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected

🐘wp-cli/wp-cli

Real-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

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.

Patches

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:

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.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`wp-cli/wp-cli`	≥ 0.12.0&&< 2.5.0	2.5.0`composer require wp-cli/wp-cli:^2.5.0`

Affected Products

1 product · 1 configurations

Application

wp-cliwp-cli

≥ 0.12.0 && < 2.5.0

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for wp-cli/wp-cli, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
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.

Frequently Asked Questions

### 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. ### Patches The vulnerability stems from the fact that the default behavior of `WP_CLI\Utils\http_request()` when encount